RU2675158C1 - Mixture for obtaining ceramic sacrificial material and method for obtaining ceramic sacrificial material - Google Patents

Abstract

FIELD: nuclear energy.SUBSTANCE: inventions relate to systems for ensuring the localization of the core melt of water-cooled tank-type nuclear reactors during a beyond design basis accident. Mixture for the production of ceramic sacrificial material for the melt localization device includes iron oxide, aluminum oxide, neutron moderator - gadolinium oxide and sintering activator. As an activator of sintering, the mixture contains calcium oxide, aluminum oxide, sodium oxide and boron oxide in the following ratio of components (wt. %): iron oxide 60–70, aluminum oxide 30–40, gadolinium oxide to 0.15, calcium oxide 1.0–3.5, sodium oxide 0.5–1.5, boron oxide 0.5–1.2. As a raw material containing alumina, which is part of the sintering activator, as well as a raw material, containing calcium oxide, high-alumina cement is used, and sodium tetraborate is used as a raw material containing sodium oxide and boron oxide.EFFECT: invention allows to increase the environmental safety of the ceramic sacrificial material by reducing the hazard class of the starting materials, and also reduces the energy consumption for the production of this material.10 cl, 1 tbl

Description

FIELD OF THE INVENTION

The invention relates to systems for passive protection of a nuclear reactor, and can be used to provide localization of the melt in the core of water-cooled reactor vessels in a beyond design basis accident.

In modern designs of nuclear power plants with high-power reactor facilities, one of the elements provided for the control of beyond design basis accidents (ZPA) and forming the fourth level of defense in depth is the melt localization device (ULR). It is intended to reduce to a safe level the radiation consequences of severe beyond design basis accidents, in which, during prolonged drainage of the core at low pressure in the primary circuit, it is destroyed with subsequent melting of the reactor vessel. Improving safety is achieved by eliminating the release of liquid and solid radioactive materials beyond the limits of the OHR, which ensures the exclusion of damage to the containment.

State of the art

In a beyond design basis accident, in order to ensure localization of the melt in the core of water-cooled water-cooled reactor vessels, in particular, sacrificial ceramic materials placed inside the cylindrical tank of the melt localization device are intended. In the event of an beyond design basis accident, such ceramic materials should work at high temperatures in contact with the corium, interact with the latter, changing its density, enthalpy and recovery potential. In a severe accident of a nuclear reactor with loss of coolant as a result of uncontrolled heating of the fuel elements, a melt (corium) is formed due to the melting and destruction of the fuel assemblies and internals of the nuclear reactor. Corium as the main components contains oxides of uranium and zirconium in the oxide phase, as well as uranium, zirconium and metal structures in the metal phase of the melt. After the destruction of the reactor vessel, the molten corium enters the melt localization device. [Asmolov V.G. The concept of severe accident management at WWER nuclear power plants. “Safety issues for WWER nuclear power plants. Investigation of the process during beyond design basis accidents with core destruction. ” Tr. scientific etc. seminar, St. Petersburg, September 12-14, 2000 St. Petersburg: Publishing. AEP, 2000, p. 1-22.]

Sacrificial material located directly in the OHR should in any likely accident scenario:

- reduce the enthalpy of corium;

- form unlimited solutions with a melt of the oxide phase of the corium;

- oxidize the most aggressive components of corium - metallic uranium and zirconium without the formation of gaseous reaction products;

- the solidus temperature of the multicomponent oxide melt formed after the interaction of the corium with the sacrificial material should be minimal;

- the density of sacrificial non-metallic materials should provide a decrease in the density of the formed oxide melt to values lower than the density of molten steel;

- the bulk density of the ceramic material should be high and allow sufficient free space inside the HRM to receive molten corium.

- subject to the above requirements, the sacrificial material should also have a compressive strength of at least 20 MPa to ensure the mechanical reliability of the design of the ULR.

An analysis of the principles of selecting a ceramic sacrificial material for a melt trap showed that the optimal composition for producing this material is a mixture of iron and aluminum oxides, which is close in composition to an equimolar mixture. To prevent secondary criticality, a neutron absorber was introduced into the composition, for example, gadolinium oxide Gd ₂ O ₃ , which has an abnormally high thermal neutron capture cross section. The specified sacrificial material effectively interacts with both the oxide component of corium and the metal component of corium (zirconium). [Asmolov V.G., Zagryazkin V.N., Udalov Yu.P. et al. The choice of the sacrificial material of the trap for holding the melt of the VVER-1000 core. - Atomic Energy, 2002, vol. 92, no. 1, p. 7-18].

The disadvantage of this mixture is the impossibility of obtaining a dense ceramic material at temperatures below 1350 ° C and the intensive decomposition of hematite into magnetite at higher temperatures.

There are known varieties of oxide materials for use in the considered purposes: for example, ceramic sacrificial materials based on SiO ₂ , Al ₂ O ₃ , ZrO ₂ , MgO, VO ₂ , ThO ₂ , as well as iron and aluminum oxides [US Patent 5,343,506]. However, the quantitative composition of the ceramic material and its characteristics (density, porosity, etc.) are not indicated in the patent description, and there are no justifications for the optimal composition in the patent.

The material according to US patent 5,343,506 is not able to solve one of the important functions of the sacrificial material - the oxidation of metallic zirconium and chromium in corium, since it does not contain enough oxides that can easily and in large quantities give oxygen.

Known compositions for producing ceramic materials based on iron and aluminum oxides, in which various additives are introduced as a result of high-temperature sintering to achieve the necessary density and strength. So in US patent 4,810,290 to ensure sintering of iron ore is introduced up to 2 mass. % calcium oxide CaO. For similar purposes, it is proposed to introduce up to 0.8 masses in iron ore, consisting mainly of magnetite Fe ₃ O ₄ . % alkali element silicates [US Pat. No. 6,293,994] or colloidal silica [US Pat. No. 6,384,126].

The disadvantages of such materials from the point of view of their use as sacrificial materials for the trap of a melt of a nuclear reactor include the fact that during their synthesis at high temperatures there is a partial loss of hematite oxygen with its transition to magnetite, as well as the fact that the density and strength of the ceramic material was not controlled , which leads to the impossibility of their use in the actual design of the device for localization of the melt due to the inability to use the characteristics of the material in the calculation codes justification operability melt localization device.

A known composition for producing a synthetic refractory material based on a mixture of iron and aluminum oxides with a ratio in the initial charge Fe ₂ O ₃ : Al ₂ O ₃ from 30:70 to 60:40, containing an additive of magnesium oxide MgO from 20 to 60 mass. % [Canadian patent 2379885]. This ceramic material, along with a set of properties that partially satisfy the requirements for non-metallic sacrificial materials for HRM (low melting point, solubility in an unlimited range of concentrations in the molten corium, the ability to lower the density of the corium), has the following disadvantages: the use of MgO as a sintering activating additive results in a loss of intensity oxide Fe ₂ O ₃ in the burning step transition portion of the oxygen in magnetite Fe ₃ O _4, so as to achieve sufficient strength ( elichina it is not specified in the patent) the ceramic material is fired at a temperature from 1350 to 1600 ° C. As a result, the material loses some of its valuable properties (iron oxide Fe ₂ O ₃ decomposes under these conditions to Fe ₃ O ₄ with the release of 3.1% oxygen by weight of iron oxide). In addition, the release of oxygen from Fe ₂ O ₃ at the stage of firing makes sintering difficult, which does not allow a single firing to obtain the required bulk density of the ceramic material. The reason for this behavior of hematite when using a magnesium oxide additive as a sintering activator is as follows. During the diffusion of divalent magnesium ions into the crystal lattice of ferric oxide Fe ₂ O ₃ , magnesium ions are inserted into the sites of iron ions with the formation of oxygen vacancies to compensate for the lack of charge in the cationic sublattice. As a result, a Schottky defect is formed in which the oxygen ion migrates to the surface, where it loses charge and leaves the crystal lattice with the formation of gaseous oxygen. This type of interaction is observed for all monovalent and divalent cations (which could potentially be fusible sintering activators). Cations of trivalent metals cannot be sintering activators, since, as a rule, they have a very high melting point (higher than that of iron oxide). The cations of tetravalent and pentavalent metals, in principle, can be sintering activators for trivalent iron oxide, since when they diffuse into the Fe ₂ O ₃ oxide crystal lattice, metal cations replace ferric cations with the formation of vacancies in the cationic sublattice to compensate for the excess charge (i.e. , Schottky defects are formed due to the departure of iron cations to the surface of the crystal), and the sublattice of oxygen ions remains unchanged and oxygen loss does not occur. These circumstances lead to the fact that magnesium oxide cannot be used as an effective additive in the production of sacrificial ceramic material from a mixture of iron oxide III and aluminum oxide.

The oxide material of the melt trap of the active zone of a nuclear reactor is also known, including Al ₂ O ₃ , SiO ₂ , Fe ₂ O ₃ and / or Fe ₃ O ₄ and a target additive selected from the series: Gd ₂ O ₃ , Eu ₂ O ₃ , Sm ₂ O ₃ in the following ratio of components (wt.%): Fe ₂ O ₃ and / or Fe ₃ O ₄ - 46-80, Al ₂ O ₃ - 16-50, SiO ₂ - 1-4, the target additive is 0, 1-4 [RU 2191436 C1, G21C 9/016, published October 21, 2002].

The specified oxide material allows to ensure nuclear safety of the core melt of a nuclear reactor without reducing the efficiency of localization of this melt.

The manufacturing technology of sacrificial ceramic material includes the following operations: preparation of a mixture consisting of iron, aluminum, silicon oxides and a target additive, grinding it to obtain a press powder, pressing samples and then firing them at a temperature of 1280-1300 ° C with holding for 2 hours. Then the firing product is subjected to crushing, grinding, fractionation, mixing with a temporary binder and re-pressing, followed by repeated high-temperature firing at T = 1320 ° C with holding for 6 hours. The disadvantage of this oxide material is that the technology for producing a sacrificial ceramic material based on it is characterized by rather high labor and energy costs due to the double operation of grinding and firing.

Closest to the proposed mixture for ceramic sacrificial material is a mixture that contains iron oxide 62-90 mass. %, alumina 8-33 mass. %, sintering activator - vanadium oxide or manganese oxide in an amount of 2-5 mass. % and neutron moderator - gadolinium oxide in the amount of 0.1-0.2% of the total content of iron oxide, alumina and sintering activator. The specified mixture allows to obtain a ceramic sacrificial material based on hematite Fe ₂ O ₃ and aluminum oxide Al ₂ O ₃ , which has a sufficiently high ability to oxidize the most aggressive metal components of corium, and also provides the ability to achieve a given bulk density of the ceramic sacrificial material by eliminating the release of free oxygen during sintering of the starting components (EA No. 003961 B1, published 2003.10.30, G21C 9/016).

The disadvantage of this mixture is that it uses substances of the second (vanadium oxide) and third (manganese oxide) hazard classes. Moreover, these sintering activators provide the possibility of a single firing of ceramic products at a temperature of 1280 ° C, which is a fairly high temperature and causes increased costs for special heating methods. All this makes the technology of sacrificial ceramic material of this composition environmentally unsafe and costly.

A known method of producing ceramic materials for trapping a molten core of a nuclear reactor containing iron oxide, aluminum oxide and silicon dioxide, including the preparation of a mixture with a given ratio of the starting components by grinding and mixing them. In this case, silicon dioxide and part of the aluminum oxide are introduced into the composition of the material in the form of kaolin, the content of which is 2.1-2.3 times higher than the specified content in the material of silicon dioxide, and the intensity and duration of the grinding of the charge is controlled and adjusted so that at least 99% of the charge powder particles had a size of not more than 0.063 mm. Then, the press powder is prepared from the mixture, the briquettes are pressed and then fired in air at a temperature of 1300-1380 ° C for 2-14 hours. The aged briquettes are crushed, followed by grinding and sieving the powder into fractions, and grinding is carried out, at least in two stages: with the separation of a coarse fraction with a particle size of 0.5 to 2 mm, comprising 55-65% of the powder, and a fine fraction with a particle size of not more than 0.063 mm, comprising 35-45% of the powder. The obtained powder fractions are mixed with a temporary binder and pressed, after which the resulting products are subjected to final firing at a temperature of 1200-1300 ° C in an air atmosphere with exposure for 4-14 hours (RU 2206930 C1, G21C 9/016, published on 20.06.2003 )

The specified method allows to increase the reproducibility of such physical and mechanical properties of ceramic sacrificial materials as density, porosity, thermal conductivity, strength. The final firing of the specified material at a temperature of 1200-1300 ° C allows to reduce energy consumption and the cost of its production.

The disadvantage of this method is the complex multi-partition technology, which dramatically increases the cost of sacrificial ceramic materials.

Closest to the proposed method is a method of manufacturing a ceramic sacrificial material for a device for localizing a melt of a nuclear reactor by preparing a mixture containing iron oxide, aluminum oxide, a neutron absorber - gadolinium oxide, and a sintering activator, moreover, the preparation of the mixture is carried out in two stages. First, a joint grinding of aluminum oxide, a neutron absorber and a sintering activator is performed, and then a joint grinding of all components of the charge is carried out until a powder grain size of less than 10 microns is achieved. followed by firing the obtained powder (RU 2517436 C2, G21C 9/016, published 05/27/2014).

When implementing this method, finely ground alumina and silica as an activator of sintering when heated already at 1200 ° C begin to form fine-grained mullite, which, on the one hand, prevents the formation of hercinitis (compounds FeAl ₂ O ₄ with a lower oxygen content compared to hematite Fe ₂ O ₃ ), on the other hand, increases the strength of the ceramic material. Also, the method allows to increase the residual amount of reactive oxygen in iron oxide and activates the sintering of oxides at relatively low temperatures. The method provides ceramic material with characteristics that are quite comparable with the characteristics of double firing materials both in density and in compressive strength.

The disadvantage of this method is that the temperature of a single firing is high enough - 1320 ° C, which makes the cost of sacrificial ceramic material too high, and production is economically inefficient.

SUMMARY OF THE INVENTION

The objective of the invention is to achieve a technical result consisting in the development of a mixture for the production of ceramic sacrificial material based on iron and aluminum oxides for a device for localizing the melt of the core of a water-water type nuclear reactor, which improves the environmental safety and economic efficiency of the process of obtaining ceramic sacrificial material while maintaining its functional properties, as well as the development of a method for producing ceramic sacrificial mater iala based on the specified mixture.

The technical result is achieved by a mixture to obtain a ceramic sacrificial material for a device for localizing a melt in the core of a water-type nuclear reactor, which includes iron oxide, aluminum oxide, a neutron moderator - gadolinium oxide and a sintering activator.

Moreover, according to the invention, the proposed mixture as a sintering activator contains calcium oxide, aluminum oxide, sodium oxide and boron oxide in the following ratio of components:

iron oxide 60-70 mass% aluminium oxide 30-40 mass% gadolinium oxide up to 0.15 mass% calcium oxide 1.0-3.5 mass% sodium oxide 0.5-1.5 mass% boron oxide 0.5-1.2 mass%,

moreover, high alumina cement is used as a raw material containing alumina, which is part of the sintering activator, and also as a raw material containing calcium oxide, and sodium tetraborate is used as a raw material containing sodium oxide and boron oxide.

In particular, the mixture may contain calcium oxide and aluminum oxide in the form of calcium aluminates in the composition of high-alumina cement grade VHC I or grade VHC II, while the content of high-alumina cement is not more than 10 mass%.

In particular, the mixture may contain sodium tetraborate in an amount of not more than 2.7 mass%.

In particular, the ceramic sacrificial material obtained by sintering the mixture at a temperature not exceeding 1250 ° C, can be characterized by a density of 3500-4000 kg / m ³ .

The technical result is also achieved by the method of producing ceramic sacrificial material for a device for localizing a melt in the core of a water-type nuclear reactor, including preparing a mixture of the following components: iron oxide, aluminum oxide, gadolinium oxide and a sintering activator, grinding said mixture, mixing it with a plasticizer, with subsequent pressing of the mixture and firing of the pressed products, while the preparation of the mixture is carried out by separately mixing the first and second groups of components.

According to the invention, the preparation of the first group of components is carried out by co-grinding aluminum oxide and gadolinium oxide. The preparation of the second group of components is carried out by grinding iron oxide in the presence of a sintering activator, moreover, calcium oxide, aluminum oxide, sodium oxide and boron oxide are used as a sintering activator, and high-alumina cement is used as a raw material containing calcium oxide and alumina, and sodium tetraborate is used as a raw material containing sodium oxide and boron oxide. Then carry out the mixing of the first and second groups of components with subsequent quality control of the resulting mixture according to its density. The resulting mixture is subjected to intensive mixing with an aqueous solution of a plasticizer, which is used as an organic surfactant, and this mixing is carried out until the formation of granules of uniform size with a size of not more than 2 mm The obtained granular material is subjected to pressing with a force ensuring the density of the pressed product is not less than 2800 kg / m ³ . Then the pressed product is subjected to drying to a moisture content of less than 1 mass. %, and dried products are fired at a temperature of less than 1250 ° C.

In particular, when controlling the quality of the resulting mixture, its bulk density may be 700-1300 kg / m ³ .

In particular, a Polyplast SP-1 plasticizer can be used as an organic surfactant, which is a mixture of sodium salts of polymethylene naphthalene sulfonic acids of various molecular weights, and the concentration of an aqueous solution of this plasticizer does not exceed 15 wt%.

In particular, intensive mixing with a plasticizer can be carried out in a mixer with a high-speed activator and with a rotating tank, while ensuring a mixing mode with an index of dimensionless Froude criterion of more than 10.

In particular, the obtained granular material to ensure the density of the pressed product is not less than 2800 kg / m ³ can be subjected to pressing in a hydraulic press.

In particular, the ceramic sacrificial material after firing can be characterized by a density of 3500-4000 kg / m ³ and compressive strength from 80 to 120 MPa.

The proposed mixture for producing ceramic sacrificial material and the proposed method for producing ceramic sacrificial material provide ceramic sacrificial material based on aluminum and iron oxides, which is characterized by the maximum possible amount of bound oxygen in the form of compounds based on Fe ₂ O ₃ and has a given bulk density (3500- 4000 kg / m ³ ) after a single firing at a temperature not exceeding 1250 ° C.

Given the large difference in the grindability of iron oxide and alumina, the proposed method for producing ceramic sacrificial material provides for preliminary intensive grinding of aluminum oxide and gadolinium oxide to a fineness corresponding to the size of the resulting particles less than 10 μm, as well as grinding of iron oxide in the presence of a sintering activator. Then obtained by separate grinding these mixtures are mixed with each other. Calcium oxide, alumina, sodium oxide and boron oxide are used as a sintering activator, and high alumina cement is used as a raw material containing calcium oxide and alumina, and sodium tetraborate is used as a raw material containing sodium oxide and boron oxide. . High alumina cement plays the role of both a binder and a plasticizer in the briquetting of samples, and a mineralizer - an activator of sintering. Obtaining ceramic sacrificial material with desired properties during a single high-temperature treatment is achieved by intensifying firing by introducing a mineralizer into the mixture — calcium aluminates from high-alumina cement), as well as by intensifying the firing process by using mechanical activation of the mixture to obtain ceramic sacrificial material.

The proposed mixture provides an increase in the residual amount of reactive oxygen in iron oxide and activates the sintering of iron and aluminum oxides at relatively low temperatures. The effectiveness of the proposed method is determined by the fact that finely ground sodium tetraborate, when heated already at 1000 ° C, begins to form an intergranular liquid phase, calcium aluminates from high-alumina cement are mineralizers and contribute to the formation of grains of a solid solution of hematite with aluminum oxide. These compounds contain trivalent iron cations, which guarantees an extremely high content of oxygen anions capable of oxidative reaction with corium components (mainly zirconium).

It should be noted that the use of high-alumina cement in the mixture to obtain ceramic sacrificial material reduces the proportion of pure aluminum oxide, which leads to improved economic characteristics of the proposed technical solution. It should also be noted that boron, which is part of tetraborate, additionally performs the function of a neutron moderator, which positively affects the properties of ceramic sacrificial material.

Information confirming the possibility of carrying out the invention

Example 1 (prototype)

The first group of components is prepared by co-grinding 1800 g of alumina (30 wt.%), 300 g of manganese oxide (5 wt.%) And 6.3 g of gadolinium oxide (0.2 wt.%). The second group of components is prepared by grinding 3900 g of iron oxide (64.9 wt.%). Then the first and second groups of components are mixed and the bulk density of the resulting mixture is determined, which is 1240 kg / m ³ . Then the resulting mixture is subjected to intensive mixing with 14 mass. % aqueous solution of polyvinyl alcohol (10% aqueous solution of PVA) in a mixer with a high-speed activator and a rotating tank in the mixing mode with a dimensionless Froude criterion of more than 10, while mixing is carried out to form granules of uniform size with a size of no more than 2 mm. The obtained granular material is subjected to pressing in a hydraulic press at a pressure of 100 MPa, providing a density of the pressed product of at least 2660 kg / m ³ . Pressed products are dried to a moisture content of less than 1 mass. %, and dried products are fired at a temperature of 1250 ° C. The resulting ceramic sacrificial material is characterized by a density of 3.2 g / cm ³ and a compressive strength of 80 MPa.

Example 2 (in accordance with the proposed mixture and method)

The first group of components is prepared by co-grinding 1430 g of alumina (24.5 wt.%) And 9.0 g of gadolinium oxide (0.15 wt.%). The second group of components is prepared by grinding 3780 g of iron oxide (63.0 wt.%) In the presence of 480 g (8.0 wt.%) Of high-alumina cement grade VHC II (the content of calcium oxide is 2.4 wt.% And aluminum oxide is 5.6% wt.%) And 300 g (5.0 wt.%) Sodium tetraborate (content of sodium oxide 0.9 wt.%, Boron oxide 1.8 wt.%). Then the first and second groups of components are mixed and the bulk density of the resulting mixture is determined, which is 740 kg / m ³ . Then the resulting mixture is subjected to intensive mixing with 14 mass. % by weight of solids with an aqueous solution of a plasticizer brand "Polyplast SP-1" (15% aqueous solution of a mixture of sodium salts of polymethylene naphthalene sulfonic acids of various molecular weights). The specified mixing is carried out in a mixer with a high-speed activator and a rotating tank in the mixing mode with a dimensionless Froude criterion of more than 10, and they are mixed until granules of uniform size with a size of no more than 2 mm are formed. The obtained granular material is subjected to pressing in a hydraulic press at a pressure of 38 MPa, providing a density of the pressed product of at least 2800 kg / m ³ . Pressed products are dried to a moisture content of less than 1 mass. %, and dried products are fired at a temperature of 1250 ° C. The resulting ceramic sacrificial material is characterized by a density of 3500 kg / m ³ and a compressive strength of 80 MPa.

Example 3, 4 (in accordance with the proposed mixture and method)

The preparation of ceramic sacrificial material is carried out analogously to example 2. The qualitative and quantitative composition of the mixture, the firing temperature of the dried product, as well as the characteristics of the obtained ceramic material are given in the table.

Example 5-11 (control examples).

Obtaining a ceramic sacrificial material is carried out analogously to example 1, taking into account some of the differences that are listed in the table, namely:

Example 5 - in a mixture of excess Na ₂ B ₄ O ₇ . The sample exfoliated after pressing.

Example 6 - bulk density less than 700 kg / m3. The density of the pressed sample and the density of the material after firing at 1250 ° C are lower than required, because the mixture was ground, the sintering activator (MnO ₂ ) at a temperature of 1250 ° C did not begin to fulfill its function.

Example 7 - pressing - without plasticizer. The density of the pressed sample is insufficient.

Example 8 - pressing - without plasticizer, overpressure pressing. The product exfoliated after exiting the mold.

Example 9 - the composition of the sintering activator was incorrectly selected (excess VHC-II, and sodium tetraborate is absent). The density of the pressed sample is insufficient.

Example 10 - excess sintering activator (VHC-I and sodium tetraborate when combined at the limit of the declared concentration range) leads to an overestimated density of the ceramic material, which is not recommended by the technical requirements for sacrificial materials.

Example 11 - the wrong mixture preparation scheme: grinding of the sintering activator is carried out together with aluminum oxide, gadolinium oxide and VHC-II. The density of the pressed sample is insufficient.

The proposed mixture for producing ceramic sacrificial material, as well as the proposed method, solve the problem of improving the environmental safety of these materials by reducing the hazard class of the starting materials. In addition, the proposed technical solutions can reduce energy costs for the production of ceramic materials due to a single firing of the mixture at a temperature not exceeding 1250 ° C while maintaining the functional properties of these materials.

Claims (15)

1. A mixture for producing ceramic sacrificial material for a device for localizing a melt in the core of a water-type nuclear reactor, including iron oxide, aluminum oxide, a neutron moderator - gadolinium oxide and a sintering activator, characterized in that the mixture contains calcium oxide as a sintering activator, alumina, sodium oxide and boron oxide in the following ratio of components, mass. %: iron oxide 60-70 aluminium oxide 30-40 gadolinium oxide up to 0.15 calcium oxide 1.0-3.5 sodium oxide 0.5-1.5 boron oxide 0.5-1.2 moreover, high alumina cement is used as a raw material containing alumina, which is part of the sintering activator, and also as a raw material containing calcium oxide, and sodium tetraborate is used as a raw material containing sodium oxide and boron oxide. 2. The mixture according to p. 1, characterized in that it contains calcium oxide and aluminum oxide in the form of calcium aluminates in the composition of high-alumina cement grade VHC I or grade VHC II, while the content of high-alumina cement is not more than 10 mass. % 3. The mixture according to p. 1 or 2, characterized in that it contains sodium tetraborate in an amount of not more than 2.7 mass. % 4. The mixture according to p. 1, characterized in that the ceramic sacrificial material with a density of 3500-4000 kg / m ³ obtained by sintering the mixture at a temperature not exceeding 1250 ° C. 5. A method of producing a ceramic sacrificial material for a device for localizing a core melt in a water-type nuclear reactor, comprising preparing a mixture of the following components: iron oxide, aluminum oxide, gadolinium oxide and a sintering activator, grinding said mixture, mixing it with a plasticizer, followed by pressing mixture and firing of pressed products, while the preparation of the mixture is carried out by separately mixing the first and second groups of components, characterized in that the preparation of the first group of components is carried out by co-grinding aluminum oxide and gadolinium oxide, and the preparation of the second group of components is carried out by grinding iron oxide in the presence of a sintering activator, which is used as calcium oxide, aluminum oxide, sodium oxide and boron oxide, and high-alumina cement is used as a raw material containing calcium oxide and alumina, and as a raw material containing sodium oxide and boron oxide, sodium tetraborate is used, then the first and second groups of components are mixed, followed by quality control of the resulting mixture according to its density, after which the resulting mixture is intensively mixed with an aqueous solution of a plasticizer, and an organic surfactant is used as a plasticizer, and this mixing is carried out until granules of uniform size are formed with no more than 2 mm in size, after which the obtained granular material is subjected to pressing with a force ensuring the density of the press Nogo products is not less than 2800 kg / m ^3, then the pressed product is dried to a moisture content of less than 1 wt. %, and dried products are fired at a temperature of less than 1250 ° C. 6. The method according to p. 5, characterized in that when controlling the quality of the resulting mixture, its bulk density is 700-1300 kg / m ³ . 7. The method according to p. 5 or 6, characterized in that as an organic surfactant use a plasticizer brand "Polyplast SP-1", which is a mixture of sodium salts of polymethylene naphthalene sulfonic acids of various molecular weights, and the concentration of an aqueous solution of the specified plasticizer does not exceed 15 mass % 8. The method according to p. 5, characterized in that the intensive mixing with the plasticizer is carried out in a mixer with a high-speed activator and with a rotating tank while ensuring a mixing mode with an indicator of dimensionless Froude criterion of more than 10. 9. The method according to p. 5, characterized in that the obtained granular material is subjected to pressing in a hydraulic press. 10. The method according to p. 5, characterized in that the ceramic sacrificial material after firing is characterized by a density of 3500-4000 kg / m ³ and compressive strength from 80 to 120 MPa.