RU2603020C1 - Method of making nuclear reactor pebbles - Google Patents

Abstract

FIELD: energy.

SUBSTANCE: invention relates to nuclear power, particularly to production of pebbles. Method comprises successively depositing on a fuel microsphere by pyrolysis of a gas mixture in a boiling layer a low density, high density, silicon carbide layer and outer high density coating layer. Low-density silicon carbide layer is deposited from a mixture of methyl silane and argon at concentration of methyl silane of 5-15 vol%, high-density silicon carbide layer is deposited from a mixture of argon and methyl silane with methyl silane concentration of not more than 10 vol%, silicon carbide layer is deposited from a mixture of argon and methyl silane with methyl silane concentration of not more than 5 vol%, external high-density silicon carbide layer is deposited from a mixture of methyltrichlorosilane and hydrogen at concentration of methyltrichlorosilane 1.2-1.5 vol%.

EFFECT: technical result is simplification of method for production of nuclear reactor pebbles, longer service life of fuel microspheres, as well as wider range of application for fast neutron reactors.

5 cl, 1 tbl, 5 dwg

Description

The invention relates to the field of nuclear energy, in particular to the production of microfuel (MT) nuclear reactor.

The use of microspherical fuel with protective coatings of the TRISO type (TRistructural ISOtropic - a three-structure isotropic coating of pyrocarbon and silicon carbide on fuel particles) ensures long-term operation of the reactor without rebooting, a large fuel burnup rate. In addition, maximum operational safety of the nuclear reactor is ensured, since TRISO microspherical fuel with a multilayer ceramic coating effectively retains fission products inside the fuel microspheres both under normal operating conditions and under conditions of maximum design accident with loss of coolant, when the fuel temperature can reach 1600 ° C.

When using a core of oxide fuel to bind oxygen released during fuel combustion, which, as a result of interaction with the carbon of the coatings, forms carbon oxides that create additional pressure inside the fuel microsphere, an oxygen getter is used located in close proximity to the fuel core.

Coating layers are obtained in the fluidized bed of fuel microspheres by gas-phase deposition of the pyrolysis products of hydrocarbon and silicon-containing gas mixtures diluted with argon and hydrogen.

A known method of deposition of a four-layer coating in a fluidized bed, according to which the first low-density (buffer) layer of pyrocarbon (PyC) is obtained by pyrolysis of C ₂ H ₂ at a temperature of 1250 ° C, the second high-density isotropic PyC is obtained by pyrolysis of C ₂ H ₂ -C ₃ H ₆ mixture at a temperature of 1300 ° C, the third SiC layer is obtained by pyrolysis of CH ₃ SiCl ₃ at a temperature of 1500 ° C and the fourth high-density isotropic PyC is obtained by pyrolysis of a C ₂ H ₂ -C ₃ H ₆ mixture at a temperature of 1300 ° C (Huschka N., Vugen P. Coated fuel particles: requirements and status of fabrication technology. - Nuclear Technology, V. 35, September, 1977, p. 238-24 5).

There is a method according to which the first layer of low-density pyrocarbon is precipitated by pyrolysis of a mixture of acetylene and argon with a concentration of 50 vol% at a temperature of 1450 ° C, 85-95% of the second layer of high-density pyrocarbon is precipitated by pyrolysis of a mixture of acetylene and argon with a concentration of the first 40.0-43 , 0 vol.% And a mixture of propylene and argon with a concentration of the first 30.0-27.0 vol.% At a temperature of 1300 ° C, and 5-15% of the coating precipitated by pyrolysis of a mixture of propylene and argon with a concentration of the first 5.0-10, 0 vol.% With the addition of 0.5-1.5 vol.% Methyltrichlorosilane. The third layer, made of silicon carbide, precipitated by pyrolysis of methyltrichlorosilane with a concentration in the mixture of hydrogen-argon 2.5-3.0 vol.% At a temperature of 1500 ° C. After deposition, it is treated in hydrogen at a temperature of 1750-1800 ° C for 20-30 minutes. Most of the fourth layer (90-95%) is precipitated by pyrolysis of a mixture of gases: acetylene with a concentration of 40.0-43.0 vol.%, Propylene with a concentration of 30.0-27.0 vol.% And argon at a temperature of 1300 ° C. And after the deposition of 90-95% of the thickness of the pyrocarbon coating of the fourth layer, 5-10% of the coating is precipitated by pyrolysis of propylene with a concentration of 3.0-5.0 vol.% In a mixture with hydrogen (patent RU No. 2300818, IPC G21C 3/06, 21 / 02, publ. 06/10/2007).

The disadvantage of these methods is that during the deposition of the first, second and fourth layers of the coating, combustible and explosive gases (propylene and acetylene) are used, while obtaining isotropic layers of pyrocarbon, it is necessary to control the degree of anisotropy of the coating, which, in turn, greatly depends on many technological factors . The disadvantages include the complexity of the process. In analogues there is no oxygen getter located in close proximity to the fuel microsphere.

There is a method according to which at least two alternating layers are deposited on the fuel microsphere, each series of layers containing a pyrocarbon layer in contact with the silicon carbide layer, the thickness of each layer being not more than 10 microns, and the layers being applied so that the layers are alternately applied pyrocarbon and silicon carbide. The layers are applied at temperatures above 1000 ° C (US patent No. 20090129533 A1).

The disadvantage of this method is the lack of technology for the deposition of a buffer layer, as a result of which when the fuel is in operation, the dense coating layers will quickly destroy due to the swelling of the fuel microsphere and the formation of gaseous fission products.

There is a method according to which porous carbon, pyrocarbon and silicon carbide are mixed with silicon nitride on a fuel microsphere, which includes the following operations: applying a coating containing a mixture of silicon and silicon carbide at a temperature of 1300 to 1950 ° C, followed by surface nitridation (Nuclear fuel provided with a coating. WO 2005086173 A2).

The disadvantage of this method is the complexity of the process and the extremely negative effect of a very high temperature (up to 1950 ° C) during the nitridation operation on an isotropic pyrocarbon layer.

A known method of producing a microtel of a nuclear reactor with a three-layer protective coating, which includes sequential deposition on the fuel microspheres of the coating layers in a fluidized bed, in which the first layer of low-density pyrocarbon is precipitated by pyrolysis of acetylene with a concentration of 50 vol.% In argon at a temperature of 1450 ° C, 95 -97% of the second layer of high-density isotropic pyrocarbon is precipitated by pyrolysis of a mixture of acetylene with a concentration in a mixture with argon of 40.0-43.0 vol.% And propylene with a concentration in a mixture with argon of 30.0-27.0 vol.% At a temperature of 1 300 ° C, and 5-3% of the coating of the second layer is precipitated by pyrolysis of propylene with a concentration of 20.0% by volume in an mixture with argon with the addition of 1.0-2.0% by volume of oxygen, the third layer is deposited Si ₃ Al ₃ O ₃ N _{5 is} carried out by pyrolysis of SiCl ₄ -NH ₃ -AlCl ₃ -O ₂ in a molar ratio (2.5-3.0) :( 3.0-4.0) :( 2.5-3.5) :( 1 5-3.0) (RF patent No. 2323782, IPC A63B 23/02, 21/00, publ. 10.10.2010).

The disadvantages of this method are the complexity of the process, the use to obtain the third layer of a four-component gas mixture, the composition of which is difficult to control, and any deviation in the composition will lead to the rejection of the entire batch of microtelles. In this method, there is a danger of the formation of an explosive mixture of gases, because combustible gases and oxygen are used.

A known method of manufacturing microtubules of a nuclear reactor, which consists in sequential deposition on a fuel microsphere in a fluidized bed of coatings of low-density pyrocarbon, high-density isotropic pyrocarbon, silicon carbide and high-density isotropic pyrocarbon. The latter is an outer coating. The carbide coating is applied by pyrolysis of methyltrichlorosilane in a mixture with hydrogen at a temperature of 1650 ± 25 ° C. When forming a carbide coating, a carbide layer of 1-10% thickness of the required thickness of the carbide coating is first applied. Then lower the temperature to 600-1200 ° C. The microspheres are treated with a mixture of Cl ₂ —H ₂ —Ar. After resume pyrolysis. Bring the thickness of the carbide coating to the desired thickness. Reduce the temperature to 600-1200 ° C and process the microspheres with a mixture of Cl ₂ -H ₂ -Ar (RF patent 2368965, IPC G21C 3/28, publ. 20.10.2009).

The disadvantages of this method are the complexity of the process, the use of aggressive chlorine, as well as the absence of an oxygen getter and the harmful effects of high temperature of 1650 ° C on the second layer of isotropic pyrocarbon,

The closest prototype of the proposed technical solution is the method according to which in the fluidized bed of fuel microspheres at 1450 ° C and a concentration of C ₂ H ₂ 50 vol.% The first buffer layer PyC is precipitated, at 1300 ° C from a mixture of C ₂ H ₂ (40- 43 vol.%) And C ₃ H ₆ (30-27 vol.%), The second high-density isotropic PyC layer is deposited, at a temperature of 1500 ° C the third silicon carbide layer is deposited from a mixture of CH ₃ SiCl ₃ with hydrogen, the fourth high-density isotropic PyC layer precipitated according to the regime of the second layer (DE patent No. 2626446, IPC 7 C23C 11/02).

The disadvantages of this method, as well as the previous ones, are the complexity of the process, in particular the use of a three-component, difficult to control mixture of gases when applying isotropic pyrocarbon of the second and fourth coating layers. The disadvantage is the use of explosive and explosive acetylene and explosive propylene in the preparation of pyrocarbon layers. In this method, the formation of large quantities of soot, which creates a significant load on the gas treatment system. In addition, the resulting microfuel must be washed from soot. In this method, there is no technology that allows you to get a getter that binds oxygen, which is released during the burning of oxide fuel.

Objective: to develop a method for the manufacture of microtubels of a nuclear reactor having an increased service life in the reactor and capable of withstanding the higher neutron fluence characteristic of fast neutron reactors.

EFFECT: increased technological effectiveness of the process and simplification of the method of production of microfuel nuclear reactor, as well as increased service life of fuel microspheres.

The technical result is achieved in a method of manufacturing a microtuel of a nuclear reactor, which consists in sequentially depositing a mixture of gases in a fluidized bed of a low-density, high-density layer of silicon carbide and an outer high-density coating layer onto the fuel microsphere, characterized in that the low-density layer of silicon carbide is deposited from a mixture of methylsilane and argon at a methylsilane concentration of 5-15 vol.%, a high-density layer of silicon carbide is precipitated from a mixture of methylsilane and argon at a methylsilane concentration of not more than 10 vol.% , a silicon carbide layer is precipitated from a mixture of methylsilane and argon at a methylsilane concentration of not more than 5 vol.%, an outer high-density layer of silicon carbide is precipitated from a mixture of hydrogen and methyltrichlorosilane at a concentration of the latter of 1.2-1.5 vol.%.

The low-density layer is precipitated at a temperature of 1100-1300 ° C.

High-density layer is precipitated at a temperature of 750-800 ° C.

The silicon carbide layer is precipitated at a temperature of 1050-1150 ° C.

The outer high-density layer is precipitated at a temperature of 1500 ° C.

The problem is solved by using only two-component gas mixtures for pyrolysis, moreover, one of the components is a diluent. When using such a mixture, it is much easier to control the composition, and even a small deviation in the concentration of the reagent practically does not affect the properties of the resulting coating. Upon receipt of the first three layers of the coating, a methylsilane-argon gas mixture with a maximum content of methylsilane of not more than 15% and not less than 85% argon is used, such a mixture is non-combustible and non-explosive. Only two reagents (methylsilane and methyltrichlorosilane) are used to apply all coating layers. Thus, in the claimed method got rid of explosive and explosive hydrocarbons (acetylene, propylene). During the pyrolysis of methylsilane mixtures, soot does not emit, as is the case with hydrocarbons, which means that there is no intensive overgrowing of equipment cavities with pyrolysis products, which increases the processability, since there is no need to clean the equipment from soot and to wash the soot of microtel themselves.

All protective coating layers in the inventive microtel of a nuclear reactor are made of silicon carbide, which is a radiation-resistant and heat-resistant structural material up to the fluences characteristic of fast neutron reactors. In this case, the low-density (highly porous, buffering) and high-density (sealing) layers of silicon carbide are obtained by pyrolysis of a chlorine-free compound, namely methylsilane. Methyltrichlorosilane is widely used in industry for the production of silicon carbide, during the pyrolysis of which hydrogen chloride is released as a by-product. The interaction of hydrogen chloride with the fuel microsphere results in the formation of volatile uranium compounds that contaminate all layers of protective coatings and equipment. Therefore, to obtain the first and second layers of silicon carbide, the absence of chlorine and other halogens is essential.

The simulation of the experimental design of microfuel was carried out. The possibility of such a design is confirmed by calculations that were carried out using the GOLT-v3 code developed by VNIINM JSC (Golubev I.E., Kurbakov S.M., Chernikov A.S. "Calculation and experimental studies of pyrocarbon and silicon carbide barriers of VTGR microfuel" Nuclear Energy, Volume 105, No. 1, July 2008, pp. 14-25). The code was tested on problems with an analytical solution, and also verified during benchmark calculations carried out by the IAEA in the framework of the CRP-6 project (Tecdoc 1674 “Advances in High-Temperature Gas-Cooled Reactor Fuel Technology”, IAEA, Vienna, Austria, 2012) .

For comparison, calculations were performed for two MT designs:

1) the proposed design: the fuel microsphere UO ₂ (diameter 400 μm, 20% enrichment according to U-235) coated with a silicon carbide coating consisting of four sequentially deposited (one after another) layers of silicon carbide: the first (starting from the microsphere) is low-density the (buffer) layer is porous SiC (thickness 100 μm, density 1.0 g / cm ³ ), the second layer is high-density SiC (thickness 35 μm, density 2.8 g / cm ³ ), the third layer is SiC (thickness 10 μm , density 2.0 g / cm ³ ) and the fourth (outer) layer is high-density β-SiC (thickness 40 μm, density 3.21 g / cm ³ ).

2) prototype design (TRISO type coated particle): fuel microsphere UO ₂ (diameter 400 μm, 20% enrichment according to U-235) coated with a four-layer coating: the first buffer layer is porous pyrocarbon (BPyC, thickness 100 μm, density 1.0 g / cm ³ ), the second layer is dense pyrocarbon (IPyC, thickness 35 μm, density 1.85 g / cm ³ ), the third layer is a layer of β-SiC (thickness 40 μm, density 3.21 g / cm ³ ) and the fourth (outer) layer is dense pyrocarbon (OPyC, thickness 40 μm, density 1.85 g / cm ³ ).

The calculations were carried out for the irradiation conditions characteristic of high-temperature gas reactors (HTGR):

- heat in a single core: 0.1 W;

- maximum burnup: 20% FIMA;

- maximum fast neutron fluence (E> 0.18 MeV): 4 × 10 ²⁵ m ^-2 ;

- maximum temperature of the fuel microsphere: 1250 ° C.

In FIG. Figure 1 shows plots of tangential thermal stresses at the beginning of a fuel campaign after outputting to rated power for two MT variants. From the above graphs it follows that during the initial heating in the power layer of silicon carbide in the coating of the prototype MT, tensile stresses develop, and in the proposed construction, the stresses in the external SiC power layer are of the order of -64 MPa. Such a distribution of stresses in the proposed multilayer coating design increases its resistance to the action of the internal pressure of the gaseous fission products, and, consequently, the burnup depth of the fuel increases.

In FIG. Figure 2 shows the dependences on the fluence of fast neutrons of internal pressure that develops under MT coatings during fuel burnout. From a comparison of the obtained curves for the 2 options, it follows that in the proposed design MT the final value of the gas pressure is 4 times lower than in the design of the prototype, and accordingly, the burnup depth of the fuel increases.

In FIG. Figure 3 shows the dependences of the maximum stresses in the power layers of the coating on the fluence of fast neutrons. From the graphs shown in this drawing, it follows that the stresses in the MT of the prototype at the beginning of irradiation from tensile thermal ones quickly move to the compression region, and then again to the tension region and tend to increase significantly as the fuel burns out and the gaseous fission products leave the fuel microsphere in porous SiC buffer layer. On the contrary, in the outer silicon carbide power layer, the MT coatings of the proposed design stresses are in the compression region during the entire calculation period and have a slight upward trend. From the obtained results we can conclude: the proposed MT design is promising for use in both thermal and fast neutron reactors.

In FIG. Figure 4 shows a photograph of a low-density silicon carbide layer.

In FIG. Figure 5 shows a photograph of a high-density silicon carbide layer deposited on a low-density silicon carbide layer.

To study the deposition modes of low-density and high-density layers, studies were carried out to study the pyrolysis of methylsilane-argon mixture at various temperatures, followed by studying the properties of the coatings obtained. The results are shown in table 1.

According to the results of the experiments, for the first, low-density coating layer, the regime corresponding to experiments No. 5-7 was selected. The layers obtained in these experiments have good strength and sufficient pore volume for a local capacitance. Both at a lower pyrolysis temperature of methylsilane (experiment No. 4) and at a higher (above 1300 ° C), weak coatings are obtained. For the second, high-density (gas-tight) layer, the regime corresponding to experiment No. 2 was selected. At methylsilane pyrolysis temperatures below 750 ° C, the deposition rate of the layer becomes too low, and at temperatures above 800 ° C the layer becomes gas permeable. The third coating layer is applied according to the experimental mode No. 8. The fourth coating layer is obtained according to the conditions given in experiment No. 9, which corresponds to the production of high-density silicon carbide in TRISO type coatings (DE patent No. 2626446, IPC 7 C23C 11/02). In experiments No. 3 and 4, very fragile and brittle coatings were obtained, probably this is due to the transition structure of silicon carbide containing a mixture of a dense and low-density component. The concentration of methylsilane in the pyrolysis mixture affects the density of the coating, so when receiving a low-density layer it should be in the range of 5-15% (at a concentration below 5%, the coating contains few pores, and above 15% the coating is fragile). Upon receipt of the second high-density layer, the concentration of methylsilane should not be higher than 10%, otherwise the coating becomes gas permeable. For the third layer of silicon carbide, the concentration of methylsilane should not be higher than 5%, otherwise too low-density coating is obtained.

The first low-density (buffer) layer of silicon carbide is applied directly to the oxide fuel microsphere; it, being a local volume for fission products and a swelling fuel core, also acts as an oxygen getter. Oxygen released during the operation of oxide fuel binds to a solid compound, SiC + 2O → SiO ₂ + С, as a result of which the maximum decrease in the pressure of carbon monoxide is achieved, which creates tensile stresses in the coating layers of the microsphere. Also, direct contact of silicon carbide with the fuel microsphere allows one to bind some solid fission products that are aggressive to high-density coating layers, for example, to obtain stable, refractory (1950 ° C) and diffusion-resistant palladium compounds (U-Si-Pd-C). Using a scanning electron microscope, pictures were taken of a low-density layer of silicon carbide (Fig. 4) and a high-density layer of silicon carbide deposited on a low-density (Fig. 5).

The second layer of high-density gas-tight silicon carbide seals the low-density (buffer) layer, preventing the release of gaseous fission products during the operation of the microfuel and preventing the penetration of hydrogen chloride to the fuel microsphere when applying a layer of silicon carbide from methyltrichlorosilane. When applying high-density silicon carbide to a porous layer, part of it penetrates into the pores. Thus, a smooth transition is created from the porous layer to the dense. Such a transition reduces mechanical stresses caused by temperature changes and radiation changes in layers of various structures.

The third layer of silicon carbide is a layer between two dense layers of silicon carbide, relieving mechanical stresses caused by the different structure of these layers, and preventing the development of a through crack.

The fourth outer high-density layer of silicon carbide is applied according to the technology used in all coatings of the TRISO type.

Examples of the technical solution.

Example 1

The apparatus for coating in a fluidized bed is heated to a temperature of 1100 ° C, with an argon flow rate of 800 l / h, a batch of fuel microspheres is poured, after which a pyrolysis gas mixture is fed instead of argon.

The first low-density layer is applied by pyrolysis of a mixture of methylsilane and argon at a methylsilane concentration of 5 vol% and a total gas flow of 900 l / h at a temperature of 1100 ° C, the deposition time of the layer is 30 minutes. The second high-density layer is obtained by feeding a mixture of methylsilane with argon at a methylsilane concentration of 2 vol% and a total gas flow of 900 l / h at a temperature of 800 ° C, the deposition time of the layer is 60 minutes. The third layer of silicon carbide is precipitated by pyrolysis from a mixture of methylsilane and argon at a methylsilane concentration of 5 vol% and a total gas flow of 900 l / h at a temperature of 1100 ° C, the deposition time of the layer is 10 minutes. The fourth high-density layer is deposited from methyltrichlorosilane vapor in a hydrogen atmosphere at a concentration of methyltrichlorosilane 1.2-1.5 vol.% And a hydrogen flow rate of 900 l / h for fluidization at a temperature of 1500 ° C, the deposition time of the layer is 120 minutes.

Example 2

The apparatus for coating in a fluidized bed is heated to a temperature of 1300 ° C, with an argon flow rate of 800 l / h, a batch of fuel microspheres is poured, after which a pyrolysis gas mixture is fed instead of argon.

The first low-density layer is applied by pyrolysis of a mixture of methylsilane and argon at a methylsilane concentration of 5 vol% and a total gas flow of 900 l / h at a temperature of 1300 ° C, the deposition time of the layer is 20 minutes. The second high-density layer is obtained by feeding a mixture of methylsilane with argon at a methylsilane concentration of 10 vol.% And a total gas flow of 900 l / h at a temperature of 800 ° C, the deposition time of the layer is 30 minutes. The third layer of silicon carbide is precipitated by pyrolysis from a mixture of methylsilane and argon at a concentration of methylsilane of 2 vol% and a total gas flow of 900 l / h at a temperature of 1100 ° C, the deposition time of the layer is 20 minutes. The fourth high-density layer is deposited from methyltrichlorosilane vapor in a hydrogen atmosphere at a concentration of methyltrichlorosilane 1.2-1.5 vol.% And a hydrogen flow rate of 900 l / h for fluidization at a temperature of 1500 ° C, the deposition time of the layer is 120 minutes.

Example 3

The apparatus for coating in a fluidized bed is heated to a temperature of 1100 ° C, with an argon flow rate of 800 l / h, a batch of fuel microspheres is poured, after which a pyrolysis gas mixture is fed instead of argon.

The first low-density layer is applied by pyrolysis of a mixture of methylsilane and argon at a concentration of methylsilane of 15 vol% and a total gas flow of 900 l / h at a temperature of 1100 ° C, the deposition time of the layer is 10 minutes. The second high-density layer is obtained by feeding a mixture of methylsilane with argon at a methylsilane concentration of 10 vol.% And a total gas flow of 900 l / h at a temperature of 800 ° C, the deposition time of the layer is 30 minutes. The third layer of silicon carbide is precipitated by pyrolysis from a mixture of methylsilane and argon at a methylsilane concentration of 5 vol% and a total gas flow of 900 l / h at a temperature of 1100 ° C, the deposition time of the layer is 10 minutes. The fourth high-density layer is deposited from methyltrichlorosilane vapor in a hydrogen atmosphere at a concentration of methyltrichlorosilane 1.2-1.5 vol.% And a hydrogen flow rate of 900 l / h for fluidization at a temperature of 1500 ° C, the deposition time of the layer is 120 minutes.

Example 4

The apparatus for coating in a fluidized bed is heated to a temperature of 1100 ° C, with an argon flow rate of 800 l / h, a batch of fuel microspheres is poured, after which a pyrolysis gas mixture is fed instead of argon.

The first low-density layer is applied by pyrolysis of a mixture of methylsilane and argon at a methylsilane concentration of 10 vol% and a temperature of 1100 ° C. The total gas consumption is 900 l / h. The deposition time of the layer is 15 minutes. The second high-density layer is obtained by pyrolysis of a mixture of methylsilane with argon at a concentration of methylsilane of 10 vol.% And a temperature of 800 ° C. The total gas consumption is 900 l / h. The deposition time is 30 minutes. A third layer of silicon carbide is precipitated by pyrolysis from a mixture of methylsilane and argon at a methylsilane concentration of 5 vol% and a temperature of 1100 ° C. The total gas consumption is 900 l / h. The deposition time is 10 minutes. The fourth high-density layer is precipitated from methyltrichlorosilane vapor in a hydrogen atmosphere at a concentration of methyltrichlorosilane 1.2-1.5 vol.% And a temperature of 1500 ° C. The flow rate of hydrogen for fluidization is 900 l / h. The deposition time is 120 minutes.

Thus, a method has been developed for the production of microfuel in a nuclear reactor having a silicon carbide protective coating that is resistant to high neutron fluence. In the inventive method for the production of microfuel, pyrocarbon coating layers are not used, which means that there is no problem with ensuring the isotropy of the coating layers and soot does not form, polluting the processing equipment. In the inventive method when the deposition of layers of protective coatings are not used fire and explosive hydrocarbons. The manufacturability of microfuel production has been improved since only two-component gas mixtures are used during pyrolysis. The microfuel obtained by the present method is able (due to the first low-density layer) to bind the oxygen released during the operation of the oxide fuel, thus providing a low pressure of gaseous fission products and carbon monoxide inside the microfuel, and, accordingly, an increased service life of the microfuel in a nuclear reactor.

Claims (5)

1. A method of manufacturing a microfuel of a nuclear reactor, which consists in sequentially depositing a mixture of gases in a fluidized bed of a low-density, high-density layer of silicon carbide and an outer high-density coating layer on the fuel microsphere by pyrolysis, characterized in that the low-density layer of silicon carbide is deposited from a mixture of methylsilane and argon at a concentration methylsilane 5-15 vol.%, a high-density layer of silicon carbide precipitated from a mixture of methylsilane and argon at a concentration of methylsilane not more than 10 vol.%, a layer of silicon carbide precipitated from cm If methylsilane and argon are present at a methylsilane concentration of not more than 5 vol.%, the outer high-density layer of silicon carbide is precipitated from a mixture of methyltrichlorosilane and hydrogen at a concentration of methyltrichlorosilane 1.2-1.5 vol.%. 2. The method according to p. 1, characterized in that the low-density layer is precipitated at a temperature of 1100-1300 ° C. 3. The method according to p. 1, characterized in that the high-density layer is precipitated at a temperature of 750-800 ° C. 4. The method according to p. 1, characterized in that the silicon carbide layer is deposited at a temperature of 1050-1150 ° C. 5. The method according to p. 1, characterized in that the outer high-density layer is precipitated at a temperature of 1500 ° C.

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