CN211150113U - Safe and movable neutron source shielding device - Google Patents

Abstract

The utility model discloses a safe movable's neutron source shield assembly, including the radiation source, still: comprises three shielding layers; the three shielding layers are respectively an inner layer, a middle layer and an outer layer; through the shielding filtration of three-layer, make it have better shielding effect, and through selecting for use special material to and special material proportion make holistic structure more compact, overall structure's volume is littleer, and the quality is littleer, convenient transport removal.

Description

Safe and movable neutron source shielding device

Technical Field

The utility model relates to a neutron source shielding equipment technical field, concretely relates to safe movable's neutron source shield assembly.

Background

²⁴¹Am-Be neutron radioactive source has wide application in the fields of industry, agriculture, scientific research, medicine and the like. Because the utilization range of the neutron source is wider and wider, the physical half-life is longer, and the energies of neutron rays and gamma rays are higher, the neutron source has the advantages of being wide in utilization range, and having higher energy²⁴¹The Am-Be neutron radioactive source needs to consider the moderation and shielding of the neutron source in each stage of production, transportation, utilization, retirement and the like. Once the treatment is not good in the transportation and utilization processes, the social safety is greatly damaged.

The traditional neutron protection device generally adopts low-density hydrogen-rich materials such as paraffin and the like to fill as shielding substances, the qualified shielding effect can be achieved only when the size of a paraffin shielding tank is designed to be 120 cm × 120 cm, the weight is about 1061 kg, and the source is not beneficial to transfer, loading and unloading in the neutron transportation and experiment processes.

SUMMERY OF THE UTILITY MODEL

To the defect among the prior art, the utility model provides a safe movable's neutron source shield assembly to improve the shielding quality, reduced the volume and the quality of whole device.

The utility model provides a safe and movable neutron source shielding device, which comprises a radioactive source and three shielding layers; the three shielding layers are respectively an inner layer, a middle layer and an outer layer, the inner layer is of a spherical structure, the middle layer wraps the inner layer, and the outer layer wraps the middle layer; the radiation source is placed in the inlayer and is wrapped up completely, the inlayer is the material for metal copper, and the middle level is the material for boron-containing polyethylene, and outer material is metallic lead, and inlayer wall thickness: thickness of the middle layer: the wall thickness of the outer layer is 8:7: 3.

Preferably, the copper has a thickness of 8CM, the boron-containing polyethylene has a thickness of 7CM, and the lead has a thickness of 3 CM.

Preferably, the gap between the inner, middle and outer layers is less than 0.1 MM.

Preferably, the radioactive source is²⁴¹Am-Be neutron radioactive source.

The beneficial effects of the utility model are embodied in: the utility model discloses a shielding of three-layer is filtered, makes it have better shielding effect, and through chooseing for use special material to and special material proportion makes holistic structure more compact, and overall structure's volume is littleer, and the quality is littleer, and convenient transport removes.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the technical solutions in the prior art will be briefly described below. Throughout the drawings, like elements or portions are generally identified by like reference numerals. In the drawings, elements or portions are not necessarily drawn to scale.

Fig. 1 is a schematic structural diagram of the present invention.

In the attached figure, a radioactive source 1, an inner layer 2, a middle layer 3 and an outer layer 4.

Detailed Description

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and therefore are only examples, and the protection scope of the present invention is not limited thereby.

It is to be noted that unless otherwise specified, technical or scientific terms used herein shall have the ordinary meaning as understood by those skilled in the art to which the present invention belongs.

As shown in figure 1, the safe and movable neutron source shielding device comprises a radioactive source 1 and three shielding layers; the three shielding layers are respectively an inner layer 2, a middle layer 3 and an outer layer 4, the inner layer 2 is of a spherical structure, the middle layer 3 wraps the inner layer 2, and the outer layer 4 wraps the middle layer 3; the radiation source is placed in inlayer 2 and by complete parcel, inlayer 2 is the material for metal copper, and middle level 3 is for containing boron polyethylene material, and outer 4 materials are metal lead, and 2 wall thicknesses of inlayer: thickness of the middle layer 3: the wall thickness of the outer layer 4 is 8:7: 3. Through the shielding filtration of three-layer, make it have better shielding effect, and through selecting for use special material to and special material proportion make holistic structure more compact, overall structure's volume is littleer, and the quality is littleer, convenient transport removal.

At present, the neutron protection calculation is more complex, the radiation dose is estimated under the source exposure state according to the partial safety consideration, a simpler empirical formula is adopted for the shielding estimation of a neutron source, and the dose of the neutron source with known average energy after multilayer shielding materials is estimated according to the following formula:

in the formula, H represents radiation dose rate (Sv/S) after neutron source shielding, phi (represents neutron fluence rate distribution (cm2/S) after neutron source shielding), dH represents a conversion coefficient (10-11Gy/n (cm-2) of the neutron fluence rate and the dose rate, 3.49 is taken for a 241Am-Be neutron source, S represents radioactivity (1/S) of a radioactive source, R represents a distance (cm) from the radioactive source, ∑ n, i represents a separation section (1/cm) of a part of material with a shielding layer being i, d represents the thickness (cm) of the shielding layer, and (1+ ∑ H.t represents a correction coefficient of neutron accumulation factor, neutron flux density or neutron dose increase caused by scattering, and is related to the thickness of the shielding layer and the section ∑ H of hydrogen for a hydrogen-containing material.

The optimal material selected by the metal is obtained by calculation through the MC method and the formula as follows: copper, boron-containing polyethylene and lead. The MC method is a commonly used experimental method in the world.

According to the embodiment, the overall size of the actual protective tank is 40 cm × 40 cm, and the volume is 0.0503m³The mass is 120kg, and the external radiation dose rate of the shielding tank is less than 0.025 m Sv.h^-1On one hand, the volume and the mass of the whole device are reduced, and on the other hand, the radiation protection standard is achieved.

Preferably, the copper has a thickness of 8CM, the boron-containing polyethylene has a thickness of 7CM, and the lead has a thickness of 3 CM. By adopting a three-layer shielding structure with the total thickness of 18cm, the shielding rate for neutrons reaches 98.73%, the shielding rate for secondary gamma rays reaches 98.02%, the safety of transportation workers is guaranteed, and all radiation irradiation is kept at an extremely low level.

Preferably, the gap between the inner layer 2, the middle layer 3 and the outer layer 4 is less than 0.1 MM.

Preferably, the radioactive source is²⁴¹Am-Be neutron radioactive source.

The operation of the embodiment configured as described above is explained below:

the utility model relates to a safe and movable neutron source shielding device, which comprises a radioactive source and three shielding layers; the three shielding layers are respectively an inner layer, a middle layer and an outer layer, the inner layer is of a spherical structure, and specific components and arrangement positions (shown in figure 1) are shown. The working principle is as follows: the inner layer of the shielding device is a spherical slowing layer and is completely wrapped²⁴¹Am-Be neutron radioactive source,²⁴¹most of fast neutrons emitted by the Am-Be neutron radioactive source are moderated to a thermal energy area through the elastic scattering and inelastic scattering effects of the moderator, and in order to achieve the maximum moderating effect, the thickness of the moderating layer is adjusted so that the fluence rate of emitted neutrons in the thermal energy area is maximized. The intermediate layer is a neutron shielding layer, moderated neutrons are captured and absorbed through collision reaction of H (N, gamma) D and 14N (N, p)14C, and the outer layer is a gamma ray shielding layer.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; such modifications and substitutions do not substantially depart from the scope of the embodiments of the present invention, and are intended to be covered by the claims and the specification.

Claims (4)

1. A safe and movable neutron source shielding device comprises a radioactive source, and is characterized in that: comprises three shielding layers; the three shielding layers are respectively an inner layer, a middle layer and an outer layer, the inner layer is of a spherical structure, the middle layer wraps the inner layer, and the outer layer wraps the middle layer; the radiation source is placed in the inlayer and is wrapped up completely, the inlayer is the material for metal copper, and the middle level is the material for boron-containing polyethylene, and outer material is metallic lead, and inlayer wall thickness: thickness of the middle layer: the wall thickness of the outer layer is 8:7: 3.

2. A safe and movable neutron source shielding device according to claim 1, wherein: the thickness of copper is 8CM, the thickness of boron-containing polyethylene is 7CM, and the thickness of lead is 3 CM.

3. A safe and movable neutron source shielding device according to claim 1, wherein: the clearance among the inner layer, the middle layer and the outer layer is less than 0.1 MM.

4. A safe and movable neutron source shielding device according to claim 1, wherein: the radioactive source is²⁴¹Am-Be neutron radioactive source.

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