RU2327238C2 - Material for absorbing neutrons - Google Patents

Abstract

FIELD: nuclear technology.

SUBSTANCE: material for absorbing neutrons consists of a first component in the form of a ceramic; in which cumuli (clot) of the second component are disperse. At least one the two components contains a material which can absorb neutrons. The ceramic has a spherical shape with granules of the same size. The largest size of granules is chosen in the range from 1.9±0.1 mm to 2.9±0.1 mm. The second component is in the form of shell, supplied to each granule. The shell is made from an organic compound, filled with compounds which can absorb neutrons.

EFFECT: increased reliability of protective properties of the material for absorbing neutrons; simplification of mounting and dismantling the protective devices; provision for high looseness of material close to fluidity of liquids.

1 cl, 6 dwg

Description

FIELD OF THE INVENTION

The claimed invention relates to nuclear technology, in particular to means of protection against radiation, and more particularly to materials for the absorption of neutrons released during the nuclear reaction of radioactive materials.

State of the art

Known material intended for the conservation of premises, equipment contaminated with radionuclides. The material is a hardening composition and consists of urea-formaldehyde resin 15-30%, a foaming agent 3-4%, an acid hardener 3-4%, water - the rest (the invention is entitled "Method for preserving a room contaminated with nuclides", RF patent No. 2078388, IPC G21F 9/34, 10/08/91). The material prevents access to contaminated objects, but does not adequately protect the environment and people from radiation, which is due to the composition of the material. In addition, it is significantly difficult to dismantle the protection during the re-conservation of the premises.

Known materials (European patent applications No. 0385187 A1, 0055679 and 0016252 A1, US patent No. 4218622, application and patent of Germany DE AS 1037302 and No. 2361363, RF patent No. 2232438, G21F 1/08, 09/27/1999), which have the form sheet, foil, metal pipes, which include neutron-absorbing components or on which absorbing elements are applied using various technologies. Often, such materials are expensive, have an insufficient efficiency, have restrictions on giving them the form that is required for shielding elements.

Known neutron absorber according to US patent No. 4225467, IPC G21C 11/00, publication 09/30/1980, the Absorber consists of particles of boron carbide (at least 90% by weight) of a certain size. Around the boron carbide particles, a condensed polymer phenol aldehyde is solidified by a solid matrix.

In some cases, for example, when using an absorber in protective devices of complex configuration, it may not provide the full level of filling and, accordingly, the required level of protection. Therefore, it is necessary to use additional equipment such as vibrators.

This is due to the fact that the absorber is not loose enough due to the large specific gravity and irregular shape of the particles; therefore, dense filling of the cavities intended for its placement is not always achieved. Due to insufficient flowability, dismantling of the protection is difficult.

As the prototype of the claimed invention, the closest neutron-absorbing composite material selected in the application No. 94043808 dated December 12, 1994 for the grant of a patent of the Russian Federation for the invention under the name "Neutron-Absorbing Composite Material and Method for Producing a Material", IPC G21F 1 / 06. The material contains a homogeneous matrix of the first component, which is a ceramic material - a powder with an average particle size below 5 microns. Accumulations (clots) of the second component selected from refractory metals, molybdenum borides and B ₄ C are homogeneously dispersed in the powder. At least one of both components contains boron.

A disadvantage of the known material is not in all cases the same protective properties in different directions, as well as the difficulty of mounting and dismounting the protection in which the known material is used. Their implementation requires special technological equipment.

This is due to the fact that the shape of the particles and clots of the components, as well as the high coefficient of friction between them limit the flowability of the material, because of which its self-sealing and the required protective properties are not ensured during installation. In addition, to ensure equal protective properties in different directions in volume, thorough mixing of the components is required; the result of which is difficult to control when installing the protection. Exposure to vibrations during delivery to the installation site, as well as when using a known material as protection during transportation of active materials, can lead to a redistribution of components (even well mixed during manufacture) in terms of material volume due to a significant difference in densities. Accordingly, the protective properties of the material will change in different directions.

Therefore, after loading it into the protective device (material), it is necessary to seal it by calcination under pressure. Obviously, the extraction of compacted and sintered material is a complex and not always feasible operation.

The objective of the invention is the creation of material for the absorption of neutrons, which allows to increase the reliability of its protective properties, as well as to simplify the installation and dismantling of protective devices.

The technical result, which is achieved by the claimed invention and which contributes to the achievement of the task, is to ensure high flowability of the material, close to fluidity, both before the operation of the material and after the end of operation, as well as ensuring high mechanical resistance, uniformity in physical parameter neutron absorption.

Disclosure of invention

The essence of the invention lies in the fact that in the material for the absorption of neutrons (hereinafter referred to as the material for absorption) containing the first component, which is a ceramic, in which the clusters (clusters) of the second component are dispersed, and at least one of both components contains neutron-absorbing material according to the invention, the ceramic is made in the form of spherical-shaped granules of the same size, the largest size of which is selected from 1.9 ± 0.1 mm to 2.9 ± 0.1 mm, and the second component is made in form about the shells each granule is provided with, while the shell is made of an organic compound filled with compounds that absorb thermal neutrons.

Distinctive from the known material of the prototype are the features of the claimed invention:

- ceramics is made in the form of spherical-shaped granules of the same size, the largest size of which is selected from 1.9 ± 0.1 mm to 2.9 ± 0.1 mm;

- the second component is made in the form of a shell, which each granule is equipped with, while the shell is made of an organic compound filled with compounds that absorb thermal neutrons.

When searching, no materials similar to the claimed invention were found, one of the components of which would have the shape and dimensions that match the shape and dimensions of the ceramics of the claimed invention.

The coating known from the aforementioned US patent No. 4225467, does not perform the functions of a carrier material that absorbs neutrons.

The coating known from US Pat. No. 4,218,622 (IPC G21C 11/00, published August 19, 1980) has a different design.

Brief Description of the Drawings

Figure 1 shows a section of one element of the material for absorption.

Figure 2 shows an element of a protective device filled with material for absorption.

Figure 3 shows a variant of the use of material for absorption in reactors and other devices when it is necessary to move the controls in the protective coating without violating its integrity.

Figure 4 shows the use of material for absorption in the transport of radioactive materials collected in containers and placed in a tanker truck.

Figure 5, 6 shows a diagram of the use of material for absorption in a railway carriage, in transport containers.

The implementation of the invention

Each element of the material for absorption (Fig. 1) consists of a core 1, which is a spherical granule made of ceramic, and a shell 2 of organic composition. The shell 2 is filled with compounds 3, for example, boron or cadmium, absorbing thermal neutrons.

Ceramics has the following composition,%:

alumina (Al ₂ O ₃ ) 56 ... 60 silicon (Si) 30 ... 34 iron oxide (magnetite, Fe ₂ O ₃ ) 5 ... 8 impurities (Ti, Ca, C) no more than 3

The granules (cores 1) of the material for absorption into one protective device are chosen the same size. Material Specifications:

- the largest size (diameter) of each granule in the party is selected from a row,

(mm) 1.9 ± 0.1; 2.1 ± 0.1; 2.3 ± 0.1; 2.5 ± 0.1; 2.7 ± 0.1; 2.9 ± 0.1;

- roundness tolerance,%

relative to kernel size 1 no more than 20 density (bulk), kg / m ³ 1600 fracture under pressure 520 kg / cm ² in a closed volume,% no more than 20 linear expansion of core material 1 when heated from 0 ° to 1000 ° C relative to 1000 mm length, mm 4.31 thermal stability of core material 1, ° С not less than 1200

The shell 2 with a thickness of 0.1-0.3 mm is made of organic material, for example, phenol-formaldehyde resin.

A shell 2 filled with neutron absorbing compounds 3 is prepared as follows. Cadmium or boron-containing compounds are ground to a fraction of less than 5 microns and mixed with an organic base. This mixture is applied to the surface of each core 1.

Use material for absorption, for example, as follows. Material for absorption 6 is poured into the cavity 4 (FIG. 2) of the protective casing 5. Having good flowability, the material 6 fills the entire free space, providing a dense gapless filling and the same distribution in all directions of the 4 nuclei in the cavity 4, which inhibit neutrons, and compounds 3, reducing the neutron flux.

In the manufacture of material for absorption 6, it is easy to ensure uniform filling of the shell 2 with compounds 3. During operation, the material for absorption 6 retains the same protective properties in all directions, because Due to the certain sizes of the cores 1 and the good flowability of the material 6, a constant relative positioning of the elements of the material 6 in the protective casing 5 is ensured. Possible non-uniformity of the protective properties of an individual element of the material 6, due to the possible non-uniformity of filling of the casing 2 with compounds 3, is leveled in the layer of material 6 in the casing 5 in any direction, as consists of many elements of this material. This ensures the required degree of protection in all directions.

Material for absorption 6 is well transported by pneumatic drive when filling the protective casing 5, is well pumped out during dismantling. This property of the material for absorption in combination with heat resistance allows it to be used in the elimination of accidents by feeding to the core using pipelines.

It is very convenient to use the material for absorption in reactors and other devices (figure 3), when the movement of controls in a protective device is required. To do this, in the protection cavity 4, which is formed by the outer 7 and inner 8 shells, the material for absorption is placed 6. The controls 9 of the apparatus 10 have the ability to move in accordance with their purpose without violating the protective properties, because material 6 flows around them like a liquid.

For transportation of radioactive materials, you can, for example, collect them in a package 11 (Fig. 4), place the packages 11 in the cavity 12 of the tank truck 13 and fill the free volume of the cavity 12 with the absorption material 6. After delivery to the destination, the absorption material 6 is sprinkled by gravity from cavity 12 through the outlet hatch of the tank (not shown in the drawings) or, for example, by means of a pneumatic drive through the loading hatch (not shown in the drawings).

Figure 5 presents the transportation of packages 11 with radioactive materials by rail. The absorption material 6 is filled in containers 14, which are made of hard or easily deformable material, for example, fabric. Capacities 14 form a protective structure.

Figure 6 shows the placement of the package 11 with radioactive materials in a transport container. The package 11 is attached to the walls 15 of the container using elastic stretch marks 16, and the free space of the container is filled with absorption material 6.

Claims (1)

A neutron absorption material containing a first component, which is a ceramic, in which clusters (bunches) of the second component are dispersed, at least one of both components contains a neutron-absorbing material, characterized in that the ceramic is made in the same size spherical granules, the largest size of which is selected from 1.9 ± 0.1 to 2.9 ± 0.1 mm, and the second component is made in the form of a shell, which is equipped with each granule, while the shell is made of organic tava filled compounds which absorb neutrons.

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