RU2236477C2 - Process of preparing metallic uranium from uranium production waste and equipment - Google Patents

Abstract

FIELD: power engineering.

SUBSTANCE: objective if invention is to provide a method and equipment allowing use of uranium-containing waste as starting material in continuous process cycle of manufacture of uranium metal products at lower cost and under environmentally safe conditions. Invention contemplates determining effective conventional weight portion of ²³⁵U in uranium waste in terms of an empirical equation. Waste is then dissolved and then extracted in the form of uranium oxides, uranium tetrafluoride, and uranium metal. The latter is refined after adjusting required value of conventional weight portion of ²³⁵U. Whole equipment for preparation of uranium oxides is combined in single production line and equipment for preparation of uranium tetrafluoride is lined with fluoroplastic.

EFFECT: increased process and economical efficiency.

19 cl

Description

The invention relates to the nuclear industry and may find application in enterprises for the production of fuel for nuclear power reactors.

The problem of uranium regeneration from uranium production wastes and the return of uranium to the process is of great importance due to the high cost of uranium and, as a result, compact uranium metal wastes are returned to the uranium smelting process. In most cases, the recovery of uranium from waste is carried out by hydrometallurgical methods, treatment with acid solutions, sorption or extraction purification and return of uranium to one of the stages of the main technological process.

There is a method of fluoride processing of uranium-containing waste, based on the conversion of uranium waste by various methods to technical uranium oxides, which are fluorinated to uranium hexafluoride (see N.P. Galkin, A.A. Mayorov, etc. Chemistry and technology of uranium fluoride compounds. M. : Gosatomizdat, 1961, p. 173-176).

The disadvantage of this method is the large number of operations and the complexity of the hardware design, since for each type it is necessary to develop an independent technology, which will inevitably lead to a rise in the cost of manufactured products from uranium metal.

There is also known a method and equipment for processing scrap and uranium waste by the extraction method, including burning combustible uranium-containing materials, transferring solid waste containing uranium to a solution when dissolved with nitric acid, and purifying uranium by extraction to obtain pure compounds suitable for use in the current production (see A. A. Mayorov, I. B. Braverman, Technology for the production of ceramic uranium dioxide powders (Moscow: Energoatomizdat, 1985, pp. 119-121).

The main disadvantage of this method and equipment is that they allow you to process certain types of uranium-containing waste and are not intended to involve all waste generated in the manufacturing process of uranium products into the main technological process.

An object of the invention is to provide a method and equipment to ensure the use of uranium-containing waste as a feedstock in the continuous technological cycle of manufacturing products from metal uranium, as well as to reduce the cost and environmental hazard of production.

The problem is solved in that uranium-containing wastes are used as feedstock, which are processed by known methods by including equipment in a continuous unified technological cycle for manufacturing products from metal uranium. In this case, the conditional mass fraction of U _{235 is} determined by the calculation method by the formula:

where C _5calc. - estimated conditional mass fraction of U ₂₃₅ in the mixture of uranium isotopes in the first sample of waste,%;

FROM $\genfrac{}{}{0ex}{}{\text{I}}{\text{5}}$ - conditional mass fraction of U ₂₃₅ in a mixture of uranium isotopes in the first sample of waste,%;

FROM $\genfrac{}{}{0ex}{}{\text{I}}{\text{0}}$ - the proportion of the mixture of uranium isotopes in the first sample of waste,%;

FROM $\genfrac{}{}{0ex}{}{\text{2}}{\text{0}}$ - the proportion of the mixture of uranium isotopes in the second sample of waste,%;

FROM $\genfrac{}{}{0ex}{}{\text{2}}{\text{5}}$ - conditional mass fraction of U ₂₃₅ in the mixture of uranium isotopes in the second sample of waste,%;

FROM $\genfrac{}{}{0ex}{}{\text{n}}{\text{5}}$ - conditional mass fraction of U ₂₃₅ in a mixture of uranium isotopes in the n-th sample of waste,%;

FROM $\genfrac{}{}{0ex}{}{\text{n}}{\text{0}}$ - the proportion of the mixture of uranium isotopes in the n-th sample of waste,%;

m _I , m ₂ , m _n - mass of uranium waste in the first, second and n-th sample of waste, respectively, g,

and before refining, it is correlated to the desired value by the formula:

where C _5treb. - the required value of the conditional mass fraction of U ₂₃₅ in the mixture of uranium isotopes of metallic uranium,%;

FROM $\genfrac{}{}{0ex}{}{\text{1}}{\text{5}}$ - conditional mass fraction of U ₂₃₅ in the mixture of uranium isotopes (high) in the first batch of uranium metal,%;

FROM $\genfrac{}{}{0ex}{}{\text{2}}{\text{5}}$ - conditional mass fraction of U ₂₃₅ in the mixture of uranium isotopes (low) in the second batch of metallic uranium,%;

m ₁ , m ₂ - weight of the first and second batches of metallic uranium, respectively, g.

The technical result of the method is achieved to the greatest extent under the following conditions:

combustible materials containing uranium, uranium metal production wastes and uranium metal chips are burned;

estimates and stripping from the production of oxide-oxide, dioxide and tetrafluoride of uranium are calcined at a temperature of 450-650 ° C;

the dissolution of uranium waste is carried out in concentrated nitric acid using deionized water at a temperature of 70-90 ° C to a concentration of uranium in solution from 150 to 250 g / l;

calcination of ammonium diuranate is carried out at a temperature of up to 350 ° C;

the dissolution of uranium dioxide is carried out in concentrated hydrochloric acid using deionized water at temperatures up to 70 ° C;

the precipitation of uranium tetrafluoride from the solution is carried out by a dosed supply of 40% hydrofluoric acid at a temperature of 50-60 ° C for 2-3 hours;

preliminary drying of uranium tetrafluoride to a powder state is carried out under incandescent lamps with a capacity of 1000-1500 kW at a temperature of 40-60 ° C;

the final drying and calcination of uranium tetrafluoride is carried out in hydrogen furnaces in two stages:

at a temperature of 110-250 ° C for 1.5-5.5 hours;

at temperatures up to 550 ° C for 1.0-3.5 hours with a hydrogen flow of 10-20 l / min;

in the thermal reduction of uranium metal, granular calcium is used;

machining of ingots of metal uranium is carried out with a spindle speed of 25-150 min ^-1 and a cutting depth of up to 3 mm;

etching of metal uranium products is carried out in nitric acid;

the packaging of metal uranium products in plastic bags is carried out in an inert environment using argon and nitrogen.

The technical problem of the method and equipment is also solved by the fact that the equipment for producing uranium oxide-oxide is interconnected into a single continuous production line and consists of a solvent reactor, filtration units, extractor stripper, calcination furnace, and a reactor for the precipitation of ammonium diuranate.

The technical result of the method and equipment according to the invention is achieved under the following conditions:

equipment lined with fluoroplastic;

filtration plants contain nutsche filters made of vinyl plastic;

the movement of uranium-containing products between technological operations is carried out in a nuclear-safe container;

equipment manufactured in nuclear safe geometry;

Uranium is calcined and dried in graphite crucibles;

the equipment is located in the following sequence: uranium combustion and calcination units, a solvent reactor, a filtration unit, extractor strippers, a filtration unit, an annealing furnace, a rotary hydrogen furnace, a large rotary tube furnace (hereinafter referred to as the BVTP furnace), a sliding furnace, a solvent reactor , filtration unit, hydrogen furnace, calcium thermal reduction unit, vacuum refining furnace, lathe, etching baths, packaging installation.

The specified set of features is new and has an inventive step, since it allows the use of uranium-containing waste as a feedstock to produce metallic uranium with the required values for uranium and uranium-235 and, as a result, reduces the cost of manufacturing products from metallic uranium by involving uranium-containing waste in the process product manufacturing cycle. The location of the equipment in a continuous unified technological line in compliance with the indicated sequence allows to minimize dusting operations and thereby reduce the environmental hazard of uranium production.

An example implementation of the method.

The technological process of the method and equipment for processing uranium-containing waste includes preparation of feedstock, production of uranium oxide, production of uranium dioxide, production of uranium hexafluoride, production of metallic uranium, refinement of metallic uranium, manufacture and control of ingots, packaging of manufactured ingots.

Preparation of feedstock from uranium-containing waste includes the following operations:

burning in an electric furnace of combustible materials containing uranium, metal uranium production waste (slag, pieces of metal uranium, etc.) and uranium metal shavings;

calcination in an electric furnace at a temperature of 450-650 ° C of the estimate and stripping from the production of oxide-oxide, dioxide and tetrafluoride of uranium;

control of uranium and uranium-235 content in a prepared batch;

determination by calculation method according to formula (1) the conditional mass fraction of uranium-235 in the batch blending of the feedstock;

the formation of batches from prepared batches of uranium-containing waste for dissolution on the basis of the above calculation with the receipt of the charge with the calculated mass fraction of uranium-235.

Uranium oxide is obtained according to the standard scheme of the ammonium diuranate process (ADU process) by precipitation of ammonium diuranate from nitrate solutions and consists of the following operations:

dissolution in the reactor at t = 80 ° C to a concentration of 150-250 g / l of prepared batches of uranium-containing waste in uranium;

filtration by suction filter of the obtained uranium solutions;

extraction-stripping with precipitation of crystals of ammonium diuranate in reactors;

filtering crystals of ammonium diuranate on a suction filter with the return of the mother liquor containing uranium to the uranium dissolution reactor;

calcination to t = 350 ° C of ammonium diuranate crystals in sliding furnaces in graphite trays;

monitoring the content of total uranium, uranium-235 and the formation of batches of feedstock of uranium oxide for the manufacture of uranium dioxide.

All technological waste in the form of oxide-oxide estimates, stripping from the production of ammonium diuranate and combustible materials (sheets, filters, rags, etc.) contaminated with uranium are returned to the operation of preparing the feedstock.

Uranium dioxide from uranium oxide is obtained by supplying hydrogen to a rotary kiln using graphite trays.

All technological waste in the form of estimates of uranium dioxide is returned to the operation of preparing the feedstock.

Uranium hexafluoride is obtained from uranium dioxide, which is dissolved in a reactor in hydrochloric acid at t = 70 ° C using deionized water, and the precipitation of uranium tetrafluoride is carried out by a dosed supply of 40% hydrofluoric acid at t = 50-60 ° C for 2- 3 hours to ensure the necessary granular composition and fluidity of crystals of uranium tetrafluoride. All liquid waste (mother liquor) containing uranium is returned to the dissolution unit.

Preliminary drying of the crystals of uranium tetrafluoride to a powder state is carried out at t = 40-60 ° C in graphite trays using incandescent lamps with a capacity of 1000-15000 kW. The use of graphite pallets makes it possible to ensure the required purity of the obtained uranium tetrafluoride by impurities of iron, chromium, nickel, the amount of which should not exceed 0.4% (wt.).

The final drying and calcination is carried out in hydrogen furnaces in two stages: at t = 110-250 ° C for 1.5-5.5 hours and t up to 550 ° C for 1.0-3.5 hours. The hydrogen consumption in this case is 10-20 l / min.

All technological waste in the form of estimates of uranium tetrafluoride is returned to the operation of preparing the feedstock.

Uranium metal ingots are obtained by the thermal method from uranium tetrafluoride using granular calcium in a calcium thermal reduction unit.

The use of granular calcium in the form of granules makes it possible to increase the yield of metallic uranium with a decrease in consequence of this amount of uranium in the resulting slag from uranium production. All technological waste in the form of slag from the production of uranium metal is returned to the operation of preparing the feedstock.

The refining of metallic uranium is carried out in a high-frequency vacuum furnace at t up to 1500 ° C for an hour. Before refining, the conditional mass fraction of uranium-235 in a mixture of uranium isotopes is determined by the formula (2) in batches of uranium metal to obtain metallic uranium with the desired value of the conditional mass fraction of uranium-235 in a mixture of uranium isotopes. All technological waste from the refining of uranium metal is returned to the operation of preparing the feedstock.

The manufacture of commodity ingots in accordance with normative and technical documentation (NTD) is carried out on a lathe with a spindle speed of 25-150 min ^-1 and a cutting depth of up to 3 mm. Uranium metal shavings are returned to the feedstock preparation operation.

The control of commodity ingots of metallic uranium for the content of impurities and uranium is carried out by the spectral method.

Packing of metal ingots after etching in nitric acid and monitoring for compliance with regulatory and technical documentation is carried out in an inert atmosphere in sealed plastic bags that are packed in a shipping container for shipment to the consumer.

Using the proposed method and equipment will allow the use of waste materials generated in the manufacturing process of products from metal uranium, which reduces the cost of manufactured products due to the low cost of uranium-containing waste, eliminate marriage in the production of metal uranium through the use of calculation methods in the preparation of uranium waste for dissolution and before refining to obtain products from uranium with the required values for total uranium and uranium-235, etc. months, and also reduce as a result of this the technological cycle of production and reduce the cost of manufacturing products from metal uranium, create a continuous technological line for the manufacture of products from metal uranium with a closed technological cycle of processing the resulting technological uranium-containing waste, which will reduce dust-generating operations and reduce this environmental hazard of uranium production.

These advantages will find expression in specific technical and economic indicators in the manufacture of products from metallic uranium.

Claims (19)

1. A method of manufacturing metallic uranium from uranium waste, including the preparation of waste, its dissolution, filtration, extraction and re-extraction, production of uranium oxide, uranium dioxide, uranium tetrafluoride and metallic uranium, refining, machining and etching of metallic uranium, control and packaging of products from it, and before preparing the waste determine the estimated conditional mass fraction of U ₂₃₅ according to the formula

where C _5calc. - estimated conditional mass fraction of U ₂₃₅ ,% in a mixture of uranium isotopes; FROM $\genfrac{}{}{0ex}{}{\text{1}}{\text{5}}$ - conditional mass fraction of U ₂₃₅ in a mixture of uranium isotopes in the first sample of waste,%; FROM $\genfrac{}{}{0ex}{}{\text{1}}{\text{0}}$ - the proportion of the mixture of uranium isotopes in the first sample of waste,%; FROM $\genfrac{}{}{0ex}{}{\text{2}}{\text{0}}$ - the proportion of the mixture of uranium isotopes in the second sample of waste,%; FROM $\genfrac{}{}{0ex}{}{\text{2}}{\text{5}}$ - conditional mass fraction of U ₂₃₅ in the mixture of uranium isotopes in the second sample of waste,%; FROM $\genfrac{}{}{0ex}{}{\text{n}}{\text{5}}$ - conditional mass fraction of U ₂₃₅ in a mixture of uranium isotopes in the nth sample of waste,%; FROM $\genfrac{}{}{0ex}{}{\text{n}}{\text{0}}$ - the proportion of the mixture of uranium isotopes in the n-th sample of waste,%; m ₁ , m ₂ , m _n - mass of uranium waste in the first, second and n-th sample of waste, respectively, g, and then, before refining, the required value of the conditional mass fraction of U ₂₃₅ in the mixture of uranium isotopes in metallic uranium is determined by the formula

where C _5treb. - the required value of the conditional mass fraction of U ₂₃₅ in the mixture of uranium isotopes of metallic uranium,%; FROM $\genfrac{}{}{0ex}{}{\text{1}}{\text{5}}$ - conditional mass fraction of U ₂₃₅ in the mixture of uranium isotopes for increased enrichment in the first batch of uranium metal,%; FROM $\genfrac{}{}{0ex}{}{\text{2}}{\text{5}}$ - conditional mass fraction of U ₂₃₅ in the mixture of uranium isotopes for reduced enrichment in the second batch of uranium metal,%; m ₁ , m ₂ - weight of the first and second batches of metallic uranium, respectively, g. 2. The method according to claim 1, characterized in that before using uranium waste as a feedstock, combustible materials containing uranium, metal uranium production waste and uranium metal shavings are burned. 3. The method according to claim 1, characterized in that before using the uranium waste as a raw material, estimates and stripping from the production of oxide-oxide, dioxide and uranium tetrafluoride are calcined at a temperature of 450-650 ° C. 4. The method according to claim 1, characterized in that in the production of uranium oxide-uranium, dissolution of uranium waste is carried out in concentrated nitric acid using deionized water at a temperature of 70-90 ° C to a uranium concentration of 50-70 g / l and residual acidity in solution from 150 to 250 g / l. 5. The method according to claims 1 and 4, characterized in that in the production of uranium oxide-uranium, the calcination of ammonium diuranate is carried out at a temperature of 600-650 ° C. 6. The method according to claim 1, characterized in that in the production of uranium tetrafluoride, dissolution of uranium dioxide is carried out in concentrated hydrochloric acid using deionized water at a temperature of up to 70 ° C. 7. The method according to claim 1, characterized in that the precipitation of uranium tetrafluoride from the solution is carried out by a dosed supply of 40% hydrofluoric acid at a temperature of 50-60 ° C for 2-3 hours 8. The method according to PP.1, 6 and 7, characterized in that the preliminary drying of uranium tetrafluoride to a powder state is carried out under incandescent lamps with a capacity of 1000-1500 kW at a temperature of 40-60 ° C. 9. The method according to claims 1, 6-8, characterized in that the final drying and calcination of uranium tetrafluoride is carried out in hydrogen furnaces in two stages: at a temperature of 110-250 ° C for 1.5-5.5 hours; at temperatures up to 550 ° C for 1.0-3.5 hours with a hydrogen flow rate of 10-20 l / min. 10. The method according to claims 1 to 9, characterized in that during the thermal reduction of metallic uranium, granular calcium is used with a granule size of 1-3 mm. 11. The method according to claims 1-10, characterized in that the machining of ingots of metal uranium is carried out with a spindle speed of 25-150 min ^-1 and a cutting depth of up to 3 mm. 12. The method according to claims 1 to 11, characterized in that the etching of products from metallic uranium is carried out in nitric acid, followed by washing in deionized water. 13. The method according to claims 1-12, characterized in that the packaging of metal uranium products in plastic bags is carried out in an inert gas environment using argon or nitrogen. 14. Equipment for the manufacture of metal uranium from uranium waste, including installations for burning and calcining uranium waste, solvent reactors, extractor strippers, ammonium diuranate precipitation reactor, uranium tetrafluoride precipitation reactor, mixers, solution containers, containers, filtration units, drying and calcining furnaces, hydrogen furnaces, uranium calcium thermal reduction unit, vacuum refining furnace, lathe, etching baths, control units and packaging, moreover, the equipment for producing uranium oxide-uranium oxide consists of a solvent reactor, filtration plants, extractor reextractor, ammonium diuranate precipitation reactor and annealing furnace connected in a single continuous production line, and uranium tetrafluoride production equipment including a precipitation reactor and a stirrer , solution containers, containers for tetrafluoride, lined with fluoroplastic. 15. Equipment according to claim 14, characterized in that the filtration units comprise nutsche filters made of vinyl plastic. 16. Equipment according to claims 14 and 15, characterized in that the movement of uranium-containing products between technological operations is carried out in a nuclear-safe container. 17. Equipment according to claims 14-16, characterized in that it is manufactured in a nuclear-safe geometry. 18. Equipment according to claims 14-17, characterized in that the calcination and drying of uranium tetrafluoride is carried out in graphite crucibles. 19. The equipment according to claims 14-18, characterized in that it is located in the following sequence: uranium production waste incineration and calcination units, a solvent reactor, a filtration unit, stripping extractors, an ammonium diuranate precipitation reactor, a uranium tetrafluoride precipitation reactor, solution containers, filtration unit, calcination furnace, rotary hydrogen furnace, large rotary tube furnace, sliding furnace, solvent reactor, filtration unit, hydrogen furnace, calcium thermal unit recovery, vacuum refining furnace, lathe, pickling baths, packaging installation.