RU2443645C1 - Charge to manufacture foamed glass with radiation protection properties - Google Patents

Abstract

FIELD: power engineering.

SUBSTANCE: charge for manufacturing of foamed glass contains a zeolite-containing tuff, a gasifier and a fluxing additive. The fluxing additive is a compound containing an element with radiation protection properties, such as lead, barium or bismuth, and selected from the group of oxides or salts of these elements. The ratio of components in the charge is as follows, wt %: zeolite-containing tuff - 57-84.5, gasifier - 0.5-3.0, radiation protection compound - 15-40.

EFFECT: lower temperature of charge foaming and production of foamed glass of low density with radiation protection properties.

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Description

The invention relates to the production of foam glass - an insulating product of inorganic composition with radiation-protective properties and can be used in nuclear power plants, nuclear marine and aircraft, and any other heat and power plants using radioactive materials.

It is known that radiation protective (RE) properties of specific materials are provided by the content of elements with a high atomic number in their matrices. In plants with radioactive elements, lead is traditionally most often used as a RE material: lead (in the form of sheet metal or powder filler of rubbers, plastics, synthetic resins), barium (mainly in the form of barite BaSO ₄ as a filler of plasters and concrete blocks) and materials containing bismuth or its compounds. Concrete, which simultaneously plays the role of a building material in the construction of enclosing structures, is also used as a RE material in nuclear power plants [Rules for working with radioactive substances and other sources of ionizing radiation. - M .: Nauka, 1984. - 303 s]. To attenuate γ-radiation of Cs by 2 times, the thickness of the lead plate at a γ-radiation energy of 1.0 MeV is 13 mm (Table 1, p. 241), the thickness of concrete is 129 mm (Table 3, p. 243).

The main disadvantage of the known RE materials is that they are not simultaneously insulating, therefore, when using such materials in nuclear power plants, such as nuclear power plants, in emergency situations there is a high risk of fires. In the event of a malfunction in a nuclear reactor, when control over the process of fission of radioactive nuclei is lost, intense heating of the surface of the reactor and the surrounding space begins, fires occur due to spontaneous combustion and the process acquires a tragic outcome. During the liquidation of an accident like Chernobyl, in addition to the enormous funds and efforts required for radiation disinfection, no less damage occurs due to fires.

It is known to obtain high-quality heat-insulating material of inorganic composition - foam glass with high mechanical strength from the composition of the mixture, the main component of which is natural aluminosilicate raw material zeolite-containing tuff, with the following components, wt.%: Zeolite-containing tuff - 99.85-99.75; silicon carbide - 0.15-0.25 [RF Patent No. 1708784, cl. C03C 11/00, 1989].

Such foam glass is characterized by high mechanical strength, which is important when it is used as a heat-insulating and structural material. The disadvantages of foam glass obtained from a known composition are:

- low efficiency as a RE material. It was found that in order to reduce Cs γ-radiation by 2 times, the thickness of the foam glass protective layer should be at least 300 mm, which is 2.2 times more than ordinary concrete;

- high foaming temperature of the mixture, which is 1160-1180 ° C, which may be an obstacle to its production with a shortage of energy resources;

- a limited range of density of foam glass in its lower value. The density of the foam glass obtained from the known composition of the charge is 460-520 kg / m ³ and its thermal conductivity is 0.08-1.2 W / m · K. Such a material does not fully realize the heat-insulating capabilities inherent in foam glass with a lower density. The lower the density of the porous material, the lower the thermal conductivity coefficient and, therefore, the better the insulating effect.

The closest technical solution to the claimed is the composition of the mixture to obtain foam glass, containing, wt.%: Zeolite-containing tuff - 55-78.5; gas blowing agent - 0.5-3.0; glass break - 15-30; soda ash - 6-12 [RF Patent No. 2051869, cl. C03C 11/00, 1996].

By a well-known solution, you can get foam glass with a density range of 250-610 kg / m ³ . Within the framework of the known composition of the charge, foam glass with higher heat-insulating properties can be obtained, since the lower density limit is 250 kg / m ³ , but it is also ineffective as a RE material. In addition, the melting temperature of the mixture is still quite high (900-1000 ° C). When used as fluxing components that lower the melting temperature of the mixture, glass breakage and soda ash, in the known solution it is not possible to reduce the melting temperature of the mixture to less than 900 ° C, which determines an increased energy consumption.

The present invention solves the problem of producing foam glass with RE properties and low density, and also provides energy savings in the production of foam glass by lowering the foaming temperature of the charge.

The proposed solution is implemented by introducing into the composition of the charge, instead of breaking glass and soda ash, a RE compound containing an element with RE properties, such as lead, barium or bismuth, and selected from the group of oxides or salts of these elements, which are simultaneously active melts that lower the temperature melting the mixture to 750-890 ° C. Due to the decrease in the viscosity of the melt due to these compounds, the lower density of the foam glass made from the proposed composition of the charge is reduced to 150 kg / m ³ .

The technical result is achieved by the fact that the proposed mixture for the manufacture of foam glass with radiation-protective properties, which includes a zeolite-containing tuff, a blowing agent and a fluxing agent, which is used as a compound containing an element with radiation-protective properties, such as lead, barium or bismuth, and selected from the group of oxides or salts of these elements, with the following ratio of components, wt.%: zeolite-containing tuff 57-84.5, blowing agent 0.5-3.0, radiation protective compound 15-40.

Restrictions on the content in the composition of the charge of the RE compound are due to the optimal ratio, which allows to achieve the RE properties of foam glass with a low density value. When the content of the compound with the RE properties is less than 15 wt.% RE, the properties of the foam glass deteriorate, the thickness of the heat-insulating layer from this material should increase. In addition, the heat-insulating properties of the foam glass deteriorate, since its density increases due to a decrease in the fluxing effect of the compound of this concentration. When the content of the specified compound with RE properties in the charge is more than 40 wt.%, The melt will be low viscosity and, as a result, the foam is unstable.

As a blowing agent, any compound used in the manufacture of traditional foam glass from glass powder and blowing agent can be used [Demidovich B.K. Foam glass. - Minsk: Science and Technology, 1975. - 248 p.], Which is able to form a gas phase at a foaming temperature in the range of 750-890 ° C, for example silicon carbide, crushed siliconized graphite, long-flame coals, graphite, coke, soot and any others gas-forming substances. Restrictions on the content in the charge of the blowing agent are due to the technological feasibility of optimal gas formation in the specified temperature range for foaming the composition of the charge.

The claimed temperature range of foaming the mixture of 750-890 ° C allows the manufacture of radiation-protective foam glass with a wider density range - 150-600 kg / m ³ . Foam glass with a low density value allows more efficient use of the insulating properties of products. Foam glass with a higher density value can be used as a heat-insulating structural building material with RE properties in the supporting elements of building structures and structures.

Below is an example of obtaining radiation-protective foam glass.

Example. Zeolite-containing rock is crushed in runners or crushers, crushed in a ball mill. The ground tuff is mixed with a blowing agent and with a compound containing any element from the specified group. The mixture is loaded into metal molds and heated to a foaming temperature of 750-890 ° C. Exposure at a final temperature of 15-60 minutes. Foamed material is cooled and annealed according to the generally accepted regime in the production of foam glass. Sudden cooling to 600 ° C in 1.5-2 hours and annealing in ≥8 hours.

Table 1 shows the composition of the charge, including PbO, BaO or Bi ₂ O _{3 as the} RE, and the properties of the RE foam glass, and in table 2, the composition of the charge, including salts of these elements and the properties of RE foam glass.

As follows from tables 1 and 2, from the proposed composition of the charge, it is possible to produce radiation-protective foam glass with a low density using a less energy-intensive technology.

Claims (1)

A mixture for the manufacture of foam glass with radiation-protective properties, including a zeolite-containing tuff, a blowing agent and a fluxing additive, characterized in that as a fluxing additive, a compound containing an element with radiation-protective properties, such as lead, barium or bismuth, is selected and selected from the group oxides or salts of these elements, in the following ratio of components, wt.%: zeolite-containing tuff 57-84.5, blowing agent 0.5-3.0, radiation protective compound 15-40.