RU2599670C1 - Method of uranyl nitrate solution processing to uranium oxide and nitric acid solution and device for its implementation - Google Patents

Abstract

FIELD: nuclear technology; ecology.

SUBSTANCE: invention relates to uranyl nitrate nuclear production waste converting process technology and implementation. Method of uranyl nitrate solution processing to uranium oxide and nitric acid solution involves generation of air plasma flow with the help of plasma reactor electric arc plasmatrons, introduction of uranyl nitrate solution and into plasma reactor mixing zone, decomposition of disintegrated uranyl nitrate solution in air plasma stream to triuranium octoxide and gas phase, reduction of products descending flow with tangential air flow, cooling flow in water-cooled gas-dynamic nozzle to temperature of 150-200 °C, separation of two-phase flow to obtain uranium oxides and gaseous phase in successively installed centrifugal separator and metal-ceramic filter from double-layer anisotropic metal ceramic with filtering surface pulse ejection regeneration, discharge of dispersed uranium oxides, nitrogen oxides and water vapor condensation from gaseous phase with simultaneous nitric acid recombination with the help of condenser and absorber and nitric acid concentration in evaporator.

EFFECT: invention provides effective and environmentally friendly production of high purity monodisperse triuranium octoxide and nitric acid in single-step process.

13 cl, 2 dwg, 1 tbl, 3 ex

Description

FIELD OF THE INVENTION

The invention relates to one of the stages of the nuclear fuel cycle (NFC) - to the technology and hardware design of a large-scale process for the processing of refined uranyl nitrate - a product of extraction and extraction processing of irradiated nuclear fuel in regenerative radiochemical plants. Irradiated nuclear fuel from nuclear power plants is delivered to the regeneration plant after the so-called "cooling" - exposure in the storage facilities of nuclear power plants, as a result of which the level of radioactivity decreases sharply. At the regeneration plant, uranium fission products and plutonium isotopes are separated by extraction, and uranyl nitrate is isolated at the final stage of this redistribution. This uranyl nitrate is the raw material for the subsequent redistribution - the isolation of triurano-octoxide (U ₃ O ₈ ) from it, which is then subjected to fluorination (production of uranium hexafluoride, UF ₆ ) and further synthesized UF _{6 is} sent to the uranium isotope separation plant, where re-enrichment is carried out uranium in the isotope U-235.

The problem is not just the production of triurano-octoxide (U ₃ O ₈ ) from uranyl nitrate, but a product that complies with the chemical and particle size specifications for the production of uranium hexafluoride, UF ₆ . This product - triuran-octoxide should be finely dispersed, its required technological properties are shown in the table below.

Fluorination of raw materials with larger particles is accompanied by the formation of cinder (1-2%). The specific surface of uranium oxides should be in the range of 3.6-10 m ² / g. When the specific surface is less than 3.6 m ² / g, the number of cinder and the probability of deposition of plaque on the walls of the flame reactor increases; when the specific surface is more than 10 m ² / g, “burning” of the upper part of the flame reactor is observed. The level of impurities must comply with the technical conditions, i.e. the content of limited impurities must comply with OST 95 10117-2003: OST 95 10117-2003 OST 95 10554-2000, according to which the yield of structural materials from the electrodes (copper, tungsten) should not exceed 10 ^-4 wt.%, the yield of iron from structural steel - not higher than 3 · 10 ^-4 wt.%.

State of the art

The existing technology for the conversion of uranyl nitrate obtained during the extraction-re-extraction processing of irradiated nuclear fuel at the regeneration plants of the Russian Federation is as follows. The uranyl nitrate solution is treated with ammonium hydroxide, while polyuranates, in particular ammonium diuranate, are precipitated; in this case, a mother liquor of ammonium nitrate occurs:

aq - aqueous solution, s - condensate.

Next, the precipitate of ammonium diuranate is separated by filtration from the mother liquor of ammonium nitrate, the precipitate is washed, then dried and calcined to isolate triuran-octaoxide:

This production is the so-called "chemical denitration" - exists at the regeneration plants of the Russian Federation. The mother liquor of ammonium nitrate (NH ₄ NO ₃ (aq)) is a waste product, for disposal it must be cleaned of residual uranium, which is an expensive and unprofitable operation. The mother liquor, which was repeatedly diluted to the maximum permissible concentration of uranium, was poured into a flowing water reservoir; at present, these solutions are pumped into deep reservoirs (the so-called "deep burial"), which only modifies the form, size and timing of manifestations of environmental damage.

There is also indirect economic damage from chemical denitration: nitric acid spent on the production of uranyl nitrate is irreversibly lost during the disposal of the mother liquor, i.e. during this operation, one of the main products of the chemical industry, nitric acid, is destroyed.

In the drying and calcining processes, gas emissions arise, which must be cleaned of technological uranium dust.

A known method of producing fine metal oxides (AS USSR No. 452177 from 08/07/1974. Yu. N. Tumanov, NP Galkin, Yu.P. Butylkin, VP Korobtsev, VA Khokhlov, G .A. Battery), in which a disintegrated metal nitrate solution - uranyl nitrate was mixed in a plasma reactor with a stream of chemically compatible air or nitrogen plasma, as a result of which the solution decomposed into dispersed metal oxides, nitrogen oxides and water vapor. The process of decomposition of a nitrate solution as applied to uranium is schematically described in general terms by the gross equation:

Drops of a disintegrated solution were kept in a plasma reactor for 10 ⁻³ −10 ⁻¹ s at a droplet size of 5 × 10 ⁻³ −1 −1 · 10 ⁻⁴ cm. Plasma flows were directed at an angle of 60 ° to the axis of the reactor. At the exit from the plasma reactor, dispersed metal oxides were separated from the gas phase at a temperature exceeding the stability temperature of the initial nitrate.

This method is implemented in relation to the production of uranium oxide - triuran-octaoxide (U ₃ O ₈ ) by decomposition of uranyl nitrate at the level of a pilot plant with a 300 kW plasma reactor and a productivity of 10-30 kg U / h (depending on the concentration of the solution in uranium (Yu .N. Tumanov. "Plasma, high-frequency, microwave and laser technologies in chemical and metallurgical processes", M: Fizmatlit, 2010, pp. 240-253 prototype).

The main hardware elements of the pilot plant.

1. The power source of the plasma torch (rectifier with automatic current control system, high-frequency or microwave generator, etc.).

2. An electric arc plasmatron in which a stream of a chemically compatible gas solution (in the case of nitrate decomposition, air or its components - nitrogen, oxygen, depending on the required valency of the metal to be released) is converted into a low-temperature plasma stream.

3. A cooled plasma reactor, where the plasma and solution flows are mixed, and the solution decomposes according to equation (3). As a rule, a plasma reactor is equipped with several plasmatrons and one or more solution disintegrators. When using several plasmatrons and disintegrators, the mixing process and the processes of heat and mass transfer during the interaction of solution droplets with a high-temperature medium are intensified.

4. A separator and a ceramic-metal filter (MKF), in which the dispersed and gas phases are separated, after which two material streams arise: a dispersed oxide material stream, which is the target product, and a gas phase stream containing, as can be seen from equation (3), nitrogen oxides, water vapor, nitrogen and oxygen.

5. Condenser-absorber. In the condenser, forced condensation of water vapor and partial absorption of nitrogen oxides are performed, and in the absorber, recombination and absorption of nitric acid is performed. As a result, a stream of nitric acid solution leaves the unit, which is then concentrated in an evaporator and returned to the re-extraction stage of uranyl nitrate.

The chemical composition of the oxide material, its physical properties, the degree of nitric acid regeneration, and other parameters are determined, first of all, by the mode of processing the solution in the plasma and, secondly, by the mode of separation of the dispersed and gas phases.

During the tests, the following technological and equipment flaws were identified.

1. Uranium oxides condense onto the cooled wall of the plasma reactor, which is accompanied by the formation of deposits, which can ultimately lead to clogging of the reactor, a change in the thermal conductivity of the wall and its temperature regime.

2. In the process of free movement of reaction products along the technological route, uncontrolled coalescence of particles of uranium oxides and their coarsening occur, as a result of which coarse powders of uranium oxides with high bulk density and low specific surface area can form.

3. Part of the nitrogen remained in the dispersed phase — triuran-octoxide (U ₃ O ₈ ), predominantly in the form of nitrogen oxides of a recombination nature. Recombination occurs mainly at the stage of separation of dispersed uranium oxides and gas phase.

The objective of the invention is the creation of an ecological production of monodisperse triurano-octoxide of high purity and a solution of nitric acid in the conversion of nuclear waste - uranyl nitrate.

The technical result to which the invention is directed.

1. To completely eliminate the conditions for the condensation of uranium oxides on the wall of the plasma reactor and, therefore, deposits on it, which can lead to clogging of the reactor and deterioration of the temperature regime.

2. Eliminate the coalescence conditions of uranium oxides and coarsening of particles, resulting in the formation of coarse powders of uranium oxides with a high bulk density and low specific surface area.

3. Eliminate the conditions for the recombination of nitrogen oxides in the dispersed phase.

To achieve this result, a method for processing a solution of uranyl nitrate into uranium oxide and a solution of nitric acid is proposed, comprising introducing a solution of uranyl nitrate and an air plasma stream into the mixing zone of a cooled plasma reactor, decomposing a disintegrated solution of uranyl nitrate in an air plasma stream of a plasma reactor into triuran-octoxide and the gas phase, separation of uranium oxides and gas phase in a sequentially mounted centrifugal separator and cermet filter from a two-layer an zotropic cermets with pulsed ejection regeneration of the filtering surface, discharge of dispersed uranium oxides, condensation of nitrogen oxides and water vapor from the gas phase with simultaneous recombination of nitric acid and concentration of nitric acid solution, while supplying a tangential stream of compressed air to the upper part of the plasma reactor vessel behind the mixing zone and upon completion of the decomposition of the disintegrated solution of uranyl nitrate in the air plasma stream of the plasma reactor into triuran-octoxide U ₃ O ₈ and the gas phase, the resulting vertically directed two-phase stream is cooled in a water-cooled gas-dynamic nozzle to a temperature of 150-200 ° C.

Besides:

- air plasma flows are introduced into the plasma reactor at an angle of 30-40 ° to the vertical axis of the reactor,

- inject the disintegrated solution of uranyl nitrate into the oxygen plasma stream with a spray angle of not more than 45 °,

- maintain the temperature in the volume of the plasma reactor at least 1200-1500 ° C,

- on the inner wall of the body of the plasma reactor maintain a temperature of 300-400 ° C,

- the initial velocity of the tangential flow of compressed air is at least 50 m / s, the air flow rate is at least 0.4 kg / s · m ² , and the product of these values is at least 2 kg / m · s,

- the cooling rate of the flow of reaction products in the gas-dynamic nozzle is 10 ⁵ -10 ⁶ K / s.

Also, to achieve a technical result, a device for processing a solution of uranyl nitrate into uranium oxide and a solution of nitric acid is proposed, containing a plasma reactor with a double water-air cooling jacket, electric arc plasma torches installed in its upper part to generate an air plasma stream with power sources, means for supplying a uranyl nitrate solution and compressed air into the plasma reactor, and centrifugal installed during the process behind the plasma reactor eparator and a sintered metal filter of the two-layered anisotropic sintered metal with a pulsed ejection regeneration of the filter surface for separation of the components of two-phase flow - the particulate triuran-oktaoksida uranium U ₃ O ₈ and gas components nitric acid solution, means for discharging uranium oxide, a condenser for condensing nitrogen oxides and water vapor, an absorber for trapping nitric acid and an evaporation apparatus for concentrating nitric acid, while the plasma reactor is made in the form of a cylindrical core a pus and a cap in the form of a truncated cone, on the conical surface of which there are electric arc plasmatrons, the axes of which are directed downward at an angle of 20-22.5 ° to the axis of the plasma reactor, the means for supplying the uranyl nitrate solution is installed vertically in the center of the horizontal surface of the plasma reactor cap, in the upper part of the housing nozzles for tangential supply of compressed air are installed in the plasma reactor, and the lower part of the plasma reactor shell is connected to a water-cooled gas-dynamic nozzle connected a centrifugal separator.

Besides:

- arc plasma torches are located symmetrically with respect to each other around the circumference of the horizontal section of the conical surface of the cover of the plasma reactor,

- the axis of the arc plasma torches are located at an angle of 30-40 ° to the vertical axis of the reactor,

- the device contains at least three electric arc plasmatrons,

- nozzles for the tangential introduction of compressed air flows are located at an angle of 5-10 ° to the plane of the horizontal section of the plasma reactor vessel,

- a means for supplying a solution of uranyl nitrate is made in the form of a centrifugal nozzle.

Disclosure of invention

In FIG. 1 shows a schematic diagram of the implementation of the invention, where:

1 - controlled thyristor rectifiers

2 - primary electrical network

3 - feeders

4 - electric arc plasmatrons

5 - air flows

6 - pneumatic centrifugal nozzle

7 - uranyl nitrate solution

8 - cover of the plasma reactor

9 - plasma reactor vessel

10 - bottom flange of the plasma reactor vessel

11 - water-cooled gas-dynamic nozzle

12 - product pipeline

13 - stream of reaction products

14 - centrifugal separator

15 is a stream of dispersed particles of triuran-octaoxide

16 - unloading auger

17 - gas phase flow

18 - cermet filter

19 - fine powder of triuran-octoxide

20 - unloading of uranium oxides in a transport tank

21 is a stream of a gas phase consisting of nitrogen oxides and water vapor

22 - capacitor

23 is a stream of a gas phase consisting of nitrogen oxides and residual water vapor

24 - absorber

25 - exhaust gas phase N ₂ About ₂

26 - stream of nitric acid solution

27 - evaporator

28 - concentrated solution of nitric acid

In FIG. 2 shows a general diagram of a plasma reactor, where:

4 - electric arc plasmatrons

5 - air flows

6 - pneumatic centrifugal nozzle

7 - uranyl nitrate solution

8 - cover of the plasma reactor

9 - plasma reactor vessel

10 - bottom flange of the plasma reactor vessel

13 - stream of reaction products

29 - air inlet fitting

30 - water inlet fitting

31 - water outlet fitting

32 - air outlet fitting

33 - nozzles for introducing a tangential air flow

34 - air plasma

35 - disintegrated uranyl nitrate stream

Thus, the implementation of the proposed method includes the following stages:

- the establishment on the wall of the plasma reactor of the required temperature regime (300-400 ° C), in which the condensation of uranium oxide is difficult in the wall zone;

- generation of an air plasma stream using several electric arc plasmatrons located symmetrically on the cover of the plasma reactor at an angle of 30-40 ° to the axis of the reactor;

- disintegration of the uranyl nitrate solution into the air plasma flows in such a way that the spray torch covers the surface of the plasma funnel formed when the plasma flows at the entrance to the cylindrical body of the plasma reactor, which is achieved by the fact that the cone of the disintegrated stream of the uranyl nitrate solution injected into the plasma stream does not exceed 45 °;

- mixing flows of a disintegrated stream of a solution of uranyl nitrate and air plasma, the simultaneous conversion of raw materials to triuran-octoxide and the gas phase, including nitrogen oxides, water vapor, nitrogen and oxygen;

- simultaneous compression of the downward flow of the above products with a tangential flow of compressed air;

- cooling the reaction products in a vertically positioned gas-dynamic nozzle, preventing coalescence of particles and cooling them to a temperature of 150-200 ° C;

- separation of dispersed uranium oxides and gas phase in a centrifugal separator;

- fine cleaning of the gas phase from submicron particles of uranium oxides in a cermet filter from a two-layer anisotropic cermets equipped with pulsed ejection regeneration of the filter surface;

- unloading the dispersed product from all unloading elements of the equipment and sending it for further processing and subsequent disposal;

- re-synthesis of nitric acid in a series-installed capacitor and absorber;

- concentration of a solution of nitric acid in the evaporator.

The plasma reactor is made in the form of a cylindrical body 9 with a cover 8 mounted on its upper flange through a heat-resistant sealing gasket.

The body of the plasma reactor is equipped with a double cooling jacket: a water cooling jacket - outside and air cooling - inside. The case is cooled through a water inlet fitting - 30 and an air inlet fitting - 29, and discharged through a water outlet fitting - 31 and an air outlet fitting - 32. The cover 8 is also equipped with a double cooling jacket and is made in the form of a truncated cone.

Just a water-cooled wall of a plasma reactor, in principle, initiates the sticking of viscous droplets and the formation of deposits on it. Wall temperature - T _W is a very important process parameter. Ideally, the value of T _W should be close to the temperature of the production mixture, which ensures the isothermal process, reduces the likelihood of particles of the condensed phase sticking to the walls of the plasma reactor. Technically, this could be done using high-temperature heat-resistant ceramic lining of the metal walls of the plasma reactor, however, this is very difficult to accomplish because of the instability of ceramics to thermal shock and cracking, which leads to a deterioration in the chemical and particle size distribution of the product. Therefore, they refused lining the metal wall and used combined water-air cooling, in which the internal cooling jacket is cooled by air, the external by water, so that the wall of the plasma reactor from the outside is really cold, and the internal, depending on the intensity of cooling, is maintained at a temperature of 300- 400 ° C, i.e. is relatively hot. The “hot” wall reduces the thermal pressure on the walls of the plasma reactor, reduces the potential for the condensation of oxide products on the walls of the plasma reactor. The present invention proposed the implementation of all structural materials from stainless steel X18 H10T.

Three to four electric arc plasmatrons 4 (two of them are shown in Figs. 1, 2) are introduced into the plasma reactor through the conical surface of the cover 8 so that the axes of the plasmatrons and the plasma reactor intersect at an angle of 30-40 ° to each other. The plasma torches are located axisymmetrically on the reactor cover 8 (three plasma torches - at an angle of 120 ° to each other, four - at an angle of 90 °). In the selected power supply circuit, controlled thyristor rectifiers 1 are used, converting the industrial frequency current from the primary electric network 2 to direct current and connected to the plasma torches 4 by the feeder 3. Compressed air flows 5 are tangentially introduced into each of the plasma torches 4, as a result of which, in the upper part of the plasma reactor air plasma is formed 34. When using copper and tungsten electrodes of an electric arc plasma torch, the product may potentially contain impurities in a larger amount than the resolution but the current specifications. In order to reduce electrode wear by an order of magnitude, copper electrodes (cathodes and anodes) of electric arc plasmatrons are doped with zirconium (1.8% zirconium) by powder metallurgy methods. To reduce the erosion by an order of magnitude of tungsten cathodes, the latter were doped with tantalum in a laser reactor (1.9% tantalum), for example, according to patent No. 2455110 "Method for the manufacture of electric arc plasmatrons".

The uranyl nitrate stream 7 passes through a solution supply means, for example, a pneumocentrifugal nozzle 6 located in the center of the horizontal surface of the cap 8. The use of a pneumocentrifugal nozzle allows you to adjust the size of the solution droplets in a wide range. The disintegrated stream of uranyl nitrate 35 is mixed with the plasma and simultaneously decomposed according to equation (3). Mixing a solution of uranyl nitrate with plasma flows is optimal when the cone of the disintegrated stream of a solution of uranyl nitrate injected into the air plasma stream does not exceed 45 °.

The geometry of the plasma reactor — the shape of the cap, the location of the nozzle, plasmatrons, and tilt angles — allows for the movement of plasma flows and uranyl nitrate solution when they are mixed along the smallest path, which reduces the likelihood of deposits on the wall of the reactor vessel.

An additional guarantee to reduce deposits is to compress the flow of the reacting mixture and the process products by the tangential flow of gaseous air supplied through nozzles 33 installed in the upper part of the reactor vessel 9. At least 0.04 kg / s of protective gas must be supplied to 1 m ^{2 of the} inner wall of the reactor walls at a speed not less than 50 m / s. The product of these values should be at least 2 kg / m · s ² . Nozzles 33 are located tangentially to the surface of the reactor vessel 9 and are directed downward at a small angle to the horizontal (5-10 °). In fact, the first 0.1 m of reactor vessel 9 should be protected from condensation of uranium oxides.

Further, the reaction product stream 13 moves from top to bottom without touching the walls of the plasma reactor vessel 9 until it enters the water-cooled vertically located gas-dynamic nozzle 11, mounted on the lower flange of the plasma reactor 10 and on the product pipeline 12 by means of the upper and lower flanges. Intensive cooling of the stream of reaction products (3) occurs in the nozzle 11, the condensation of uranium oxides takes place, and the stream 13 becomes two-phase. During the cooling of reaction products, the physical and chemical sorption of nitrogen oxides on uranium oxide particles slows down, i.e., ultimately, the nitrogen content in uranium oxides decreases.

The nozzle is equipped with a water-cooled jacket. The nozzle parameters are designed in such a way as to ensure the cooling rate of the product stream 13 at a speed of 10 ⁵ -10 ⁶ deg. K / s At the entrance to the specified nozzle, the product stream is mainly gas; at the exit from the nozzle, the product stream is two-phase, i.e. consists of particles of uranium oxides and the gas phase. The temperature of the two-phase flow is 150-200 ° С, at which coalescence and adhesion to the particle wall no longer occur. Intensive cooling of the two-phase flow of reaction products at a given speed prevents the coalescence of triuran-octaoxide particles and allows you to adjust the particle size distribution of the product.

Cooled to 150-200 ° C, the production mixture is sent to a centrifugal separator 14 (for example, a cyclone or a vortex dust collector), in which the separation of dispersed uranium oxides and gas phase occurs. Behind the centrifugal separator 14, there is a cermet filter made of a two-layer anisotropic cermets equipped with pulsed ejection regeneration of the filter surface 18 to capture the dispersed product of uranium dioxide.

Uranium oxides 15 are discharged to a discharge means, for example, to an unloading screw 16. The gas phase stream 17 containing oxygen, residual water vapor, nitrogen oxides and nitrogen enters the sintered metal filter 18, from a two-layer anisotropic sintered metal with pulse ejection regeneration of the filter surface , in this filter, the dispersed phase of the remaining submicron particles of uranium oxides is completely captured (about 5% of the initial mass of the product); the dispersed powder of uranium oxides 19 from the cermet filter 18 is sent to the screw 16.

Uranium oxides are discharged by a screw 16 into a transport tank 20.

The stream of gas products 21, purified from the dispersed powder, is removed from the sintered metal filter 18 and sent to a condenser 22, where water vapor is condensed and nitrogen oxides are partially absorbed, then stream 23 is directed to an absorber 24, where soluble nitrogen oxides are absorbed. The gas stream (N ₂ , O ₂ ) 25 is sent, if necessary, to special ventilation equipped with ozone purification of the gas exhaust (gas exhaust 27 is also sent from the evaporator 27, and the nitric acid solution 26 is pumped to the evaporator 27, from which the concentrated nitric acid solution 28 sent to the stage of reextraction of uranyl nitrate.

The figures do not show the locking and regulating apparatus, means of supplying the components of the process and the control system.

Examples of carrying out the invention

According to the proposed method, the raw material of a radiochemical plant was processed - re-extract of uranyl nitrate by conversion in an air plasma of an electric arc discharge into triuran-octoxide and nitrous gases, which are combined with water vapor in nitric acid. The initial solution (reextract UO ₂ (NO) ₃ ) ₂ ) had the following characteristics:

reextract concentration, kg U / l  0.1-0.50 the content of HNO ₃ , kg / l  0.1-0.2

The parameters of the process and apparatus shown schematically in FIG. 1-3 and intended for processing a solution of uranyl nitrate according to the proposed method are shown below:

The technical characteristics of the pilot plant are as follows:

- total electric power of three plasmatrons EDP-109, kW up to 300 - plasma forming gas - air - total air flow in plasmatrons, nm ³ / h up to 50 - mass-average temperature of air plasma, K 3000-3500 - productivity on a solution of uranyl nitrate, l / h 20-60 - concentration of uranium in a solution of uranyl nitrate, g / l 100-500 - dispersion of uranyl nitrate, microns 100-150 - pressure in the reactor, kPa 100-150 - volumetric air flow for blowing the walls of the reactor, nm ³ / h 3.5 - the speed of the blowing air at the entrance to the reactor, m / s 52.4 - weight air flow for blowing the walls of the reactor, kg / h (kg / s) 4.5 (0.0013); - temperature of the wall of the reactor vessel, C - up to 500 - the degree of purification of gas from solid particles at the entrance to the cermet filter,% 95 - the degree of powder capture in a centrifugal separator and in the MKF,% 99.999

Construction materials: X18 H10T stainless steel is used everywhere.

Air plasma flow temperature before mixing with uranyl nitrate 3000-4000 ° C Temperature in a plasma reactor after mixing plasma with uranyl nitrate 1200-5000 The inner diameter of the plasma reactor vessel, m 0.30 The linear velocity of the reacting medium in a plasma reactor, m / s 5.28 The length of the plasma reactor from the horizontal surface of the lid to the lower flange, in m 2.5 The degree of conversion of uranyl nitrate to triuran-octoxide,% 99.999 Temperature on the inner surface of the wall of the plasma reactor vessel 330 ° C Temperature on the outer surface of the wall of the plasma reactor vessel 25 ° C

The concentration of nitric acid is summed from the amount of nitrogen oxides from the decomposed uranyl nitrate and the amount of nitrogen oxides synthesized in an electric arc in the plasma torch.

Example 1

1. Productivity for re-extract, l / h 31 2. The concentration of the re-extract, kg U / l 0.35 3. Uranium productivity, kg / h 10.85 3. Productivity for uranium oxides, kg / h 12.79 4. The total air flow in the plasmatrons, nm ³ / h fifty 7. The volume of gases leaving the plasma-chemical reactor, nm ³ / h 109.4 8. The concentration of the nitric acid solution at the outlet of the absorber 4.3% 9. The cooling rate of the flow of reaction products in a gas-dynamic nozzle 10 ^5th hail. K / s The average particle size of U ₃ O ₈ mm 0.43 Product purity according to Fe, Cu, W, Cr and other impurities - 0.6 ppm 6 · 10 ^-5% weight Power consumption 6.7 kWh / kg U The content of residual nitrogen,% 0.09

The final product - uranium oxide contains 84.89 wt.%, Of which 25.46% U ⁺⁴ . The moisture content of the obtained batches of uranium oxides was 0.1%; bulk density with utryak - 2.7 g / cm ³ ; specific surface area is 2.5 m ² / g.

The concentration of nitric acid was carried out in a standard evaporator.

Example 2

1. Reextractivity, l / h 31 2. The concentration of the reextract, kg U / l 0.39 3. Uranium productivity, kg / h 12.09 3. Productivity for uranium oxides, kg / h 14.3 4. The total air flow in the plasmatrons, nm ³ / h fifty 7. The volume of gases leaving the plasma-chemical reactor, nm ³ / h 95.0 8. The concentration of the solution of nitric acid,% 5.6 9. The cooling rate of the flow of reaction products in a gas-dynamic nozzle 8 · 10 ⁴ K / s The average particle size of U ₃ O ₈ mm 0.47 Product purity by Fe, Cu, Cr and other impurities - 0.65 ppm 6.5 · 10 ^-5% weight Power consumption 6.3 kWh / kg U The content of residual nitrogen,% 0.09

The final product - uranium oxide contains 84.89 wt.%, Of which 25.46% U ⁺⁴ . The moisture content of the obtained batches of uranium oxides was 0.1%; bulk density with utryak - 2.75 g / cm ³ ; specific surface area - 2.7 m ² / g.

Example 3

1. Reextractivity, l / h 31 2. The concentration of the reextract, kg U / l 0.48 3. Uranium productivity, kg / h 14.88 3. Productivity for uranium oxides, kg / h 17.56 4. The total air flow in the plasmatrons, nm ³ / h fifty 7. The volume of gases leaving the plasma-chemical reactor nm ³ / h 96.0 8. The concentration of the nitric acid solution 7.8% 9. The cooling rate of the flow of reaction products in a gas-dynamic nozzle 9 · 10 ⁴ , K / s The average particle size of U ₃ O ₈ mm 0.51 Product purity by Fe, Cu, Cr and other impurities - 0.43 ppm 4.3 · 10 ^-5% , weight Power consumption 5.9 kWh / kg, U The content of residual nitrogen,% 0.087

The final product - uranium oxide contains 84.89 wt.%, Of which 25.46% U ⁺⁴

The moisture content of the obtained batches of uranium oxides was 0.08%; bulk density with utryak - 2.5 g / cm ³ .

Specific surface area - 2.5 m ² / g

Thus, the combination of operations and the constructive implementation of the device for their implementation will achieve a technical result, namely, to obtain in a single cycle of processing waste from the nuclear industry - a solution of uranyl nitrate-dispersed uranium oxide in the form of triuran-octoxide with high monodispersity for further use at the stages of the nuclear fuel cycle (NFC) and a solution of nitric acid, which is a valuable product of the chemical industry, and can also be returned to the technological cycle.

Claims (13)

1. A method of processing a solution of uranyl nitrate into uranium oxide and a solution of nitric acid, comprising introducing a solution of uranyl nitrate and an air plasma stream into a mixing zone of a cooled plasma reactor, decomposing a disintegrated solution of uranyl nitrate in an air plasma stream of a plasma reactor into triuran-octoxide and a gas phase, separating uranium oxides and gas phase in a sequentially mounted centrifugal separator and cermet filter from a two-layer anisotropic cermets with pulsed ejection regeneration of the filtering surface, unloading of dispersed uranium oxides, condensation of nitrogen oxides and water vapor from the gas phase with the simultaneous recombination of nitric acid and concentration of the nitric acid solution, characterized in that the tangential stream of compressed air is supplied to the upper part of the plasma reactor vessel behind the mixing zone, and upon completion of the decomposition of the disintegrated solution of uranyl nitrate in the air plasma stream of the plasma reactor into triuran-octoxide U ₃ O ₈ and the gas phase, cool the obtained th vertically directed two-phase flow in a water-cooled gas-dynamic nozzle to a temperature of 150-200 ° С. 2. The method according to p. 1, characterized in that the air plasma flows are introduced into the plasma reactor at an angle of 30-40 ° to the vertical axis of the reactor. 3. The method according to p. 1, 2, characterized in that the disintegrated solution of uranyl nitrate is injected into the oxygen plasma stream with a spray angle of not more than 45 °. 4. The method according to p. 1, characterized in that in the volume of the plasma reactor the temperature is maintained at least 1200-1500 ° C. 5. The method according to p. 1, characterized in that on the inner wall of the housing of the plasma reactor maintain a temperature of 300-400 ° C. 6. The method according to p. 1, characterized in that the initial velocity of the tangential flow of compressed air is at least 50 m / s, the air flow rate is at least 0.4 kg / s · m ² , and the product of these values must be at least 2 kg / m · s 7. The method according to p. 1, characterized in that the cooling rate of the flow of reaction products in the gas-dynamic nozzle is 10 ⁵ -10 ⁶ deg. K / s 8. Device for processing a solution of uranyl nitrate into uranium oxide and a solution of nitric acid, containing a plasma reactor with a double water-air cooling jacket, with electric arc plasma torches installed in its upper part to generate an air plasma stream with power sources, means for supplying a solution of uranyl nitrate and compressed air to a plasma reactor, and a centrifugal separator and a cermet filter made of a two-layer a installed behind the plasma reactor during the technological process low-tropic cermets with pulsed ejection regeneration of the filtering surface for separating the components of a two-phase flow - dispersed triuran-octaoxide of uranium and gas components of a solution of nitric acid, means for discharging uranium oxide, a condenser for condensation of nitrogen oxides and water vapor, an absorber for trapping nitric acid and an evaporator for concentration nitric acid, characterized in that the plasma reactor is made in the form of a cylindrical body and a cover in the form of a truncated cone The surface of which is equipped with arc plasma torches, the axes of which are directed downward at an angle of 20-22.5 ° to the axis of the plasma reactor, the means for feeding the uranyl nitrate solution are installed vertically in the center of the horizontal surface of the plasma reactor cover, nozzles for tangential supply of compressed air are installed in the upper part of the plasma reactor housing and the lower part of the plasma reactor vessel is connected to a water-cooled gas-dynamic nozzle connected to a centrifugal separator. 9. The device according to p. 8, characterized in that the electric arc plasmatrons are located symmetrically with respect to each other around the circumference of the horizontal section of the conical surface of the lid of the plasma reactor. 10. The device according to p. 8, characterized in that the axis of the arc plasma torches are located at an angle of 30-40 ° to the vertical axis of the reactor. 11. The device according to p. 8, characterized in that it contains at least three electric arc plasmatrons. 12. The device according to p. 8, characterized in that the nozzle for the tangential introduction of compressed air flows are located at an angle of 5-10 ° to the plane of the horizontal section of the plasma reactor vessel. 13. The device according to p. 8, characterized in that the means for supplying a solution of uranyl nitrate is made in the form of a centrifugal nozzle.

Images