CN102260813A - High-strength plumbum-based material with ray and neutron comprehensive shielding effect - Google Patents

Abstract

The invention belongs to a metal-based (lead-based) shielding material with comprehensive shielding effects of X, gamma rays and neutrons, especially a shielding material with high strength, light weight and multiple shielding effects. The composition of the shielding material is: the matrix is lead-based alloy PbMgAl (Mg10%-50%, Al2%-10%, the balance is Pb, mass percentage), and boron or boride is a neutron absorber. The component distribution ratio of the shielding material is: the mass percentage of the lead-based alloy is between 90% and 99.7%, and the mass percentage of boron or boride is between 0.3% and 10%. Compared with traditional Pb-based materials, Pb/B ₄ C and lead-boron polyethylene composite materials, the lead-magnesium-aluminum-boron or boride metal matrix composite materials of the present invention not only have excellent shielding X, γ-ray and neutron Comprehensive shielding effect, and its tensile strength and Brinell hardness are much higher than the existing Pb and B or B ₄ C composite shielding materials, and the manufacturing cost is lower at the same time.

Description

High-strength lead-based material with integrated radiation and neutron shielding effect

technical field

The invention belongs to a metal-based (lead-based) shielding material with comprehensive shielding effects on X, gamma rays and neutrons and a preparation method thereof, in particular to a shielding material with high strength, light weight and multiple shielding effects and a preparation method thereof.

Background technique

With the depletion of fossil energy, nuclear energy, as a clean energy source, is expanding its application fields, and the requirements for shielding materials are getting higher and higher. Comprehensive shielding materials for X, γ-ray and neutron radiation have always been an important aspect of nuclear safety. topic.

The existing X, γ-ray and neutron comprehensive shielding materials mainly include lead-boron polyethylene, B ₄ C/Pb composite material, lead-boron concrete and boron-containing stainless steel. In the lead-boron polyethylene composite material, since polyethylene is a polymer material, the softening temperature is 130°C, resulting in poor mechanical strength and heat resistance of the lead-boron polyethylene composite material, its tensile strength is about 10MPa, and the Brinell hardness is only 3~4, which seriously restricts its application; B ₄ C/Pb composite material is formed by Pb-X (X=Sb, Sn, Ag, Au, Cr, etc.) alloy and B ₄ C reinforcement through powder metallurgy or melting casting It can be used as a material for absorbing neutrons and shielding X and γ rays, but its strength and plasticity are low. Its tensile strength is 48.2MPa and Brinell hardness is 22.13, so it cannot be used alone as a structural material, and It is difficult to prepare large-scale composite materials; lead-boron concrete is heavy, poor in mobility, and complex in composition; boron-containing stainless steel has better shielding performance against gamma rays and neutrons than iron, but due to the low boron content, neutrons The absorption effect is not ideal, and the thickness of boron-containing stainless steel has to be increased, resulting in an increase in the total weight of the shielding system, and increasing the boron content has an adverse effect on the ductility and impact resistance of boron-containing stainless steel alloys, which limits the use of boron-containing stainless steel for spent fuel storage In addition, elements such as chromium, nickel, and manganese in stainless steel are activated by neutron irradiation, and personnel must be restricted from accessing the reactor after shutdown.

Although there are various ray and neutron comprehensive shielding materials, they are all inseparable from the two basic elements of boron and lead. Boron has excellent neutron shielding properties. Lead has the strongest absorption and scattering of X, β, and γ-rays, which can shield primary and secondary γ-rays, and will not become a secondary radiation source. The combination of the two is the most ideal nuclear radiation shielding material. Therefore, compounding boron or borides with lead to develop X, γ-ray and neutron comprehensive shielding materials with multiple shielding effects, light weight and high strength characteristics, improving the mechanical properties and shielding performance of shielding materials is not only important for nuclear safety. It is an important research topic in the field and an important guarantee for the promotion of nuclear energy applications.

Contents of the invention

The technical problem to be solved by the present invention is to provide a high-strength lead-based material with integrated radiation and neutron shielding effect and its preparation method, which can make the shielding material have higher mechanical and shielding performance, more convenient processing and production, and lower manufacturing cost .

The technical solution adopted to solve the technical problem of the present invention is: the shielding material is composed of PbMgAl lead-based alloy and boron or boride.

The mass percent of the components of the shielding material is: 0.3%-10% of boron or boride, and the rest is lead-based alloy.

The mass percent of each component in the PbMgAl lead-based alloy is 10%-50% of Mg, 2%-20% of Al, and the balance is Pb.

The preparation process of the above-mentioned high-strength lead-based material with comprehensive radiation and neutron shielding effect of the present invention is as follows: firstly prepare PbMgAl lead-based alloy, and finally add boron or boride to make each component fully react to obtain a fine structure, combined Good high-strength lead-based shielding material with comprehensive shielding effect of rays and neutrons. During the preparation process, the full reaction of each component should be ensured.

Due to the huge difference in the physical and chemical properties of boron and lead, boron-lead is an immiscible alloy system, and it is difficult to evenly distribute boron or borides in lead. First, PbMgAl lead-based alloy is prepared by compounding lead, magnesium and aluminum, and the high-strength metal compound generated by Pb and Mg, Mg and Al is used to improve the strength of the lead-based alloy; then boron or boride is added to make use of Mg, Al and boron Or the mutual compatibility of borides, realize the homogenization of lead and boron, and obtain high-strength lead-magnesium-aluminum-boron or boride lead-based ray/neutron shielding materials.

The beneficial effects of the present invention are: through the addition of elements Mg, Al and boron or borides, high-strength metal compounds generated by Pb and Mg, Mg and Al are used to obtain high-strength lead-magnesium-aluminum-boron or boride lead-based Ray/neutron shielding material, its tensile strength and hardness are much higher than traditional lead alloy, Pb/B ₄ C composite material and lead-boron polyethylene, reaching 120MPa and 165HBS respectively, and the elongation is 6.87%. At the same time, it has the comprehensive shielding effect of X, γ-rays and neutrons, and the high-strength lead-magnesium-aluminum-boron or boride lead-based ray/neutron shielding material with a thickness of 20mm has the shielding rate of X-rays with energies of 65KeV, 118KeV and 250KeV Respectively reach 97.9%, 99.22% and 90.29%, effectively solve the energy between 40 ~ 88KeV "weak absorption region of Pb"problem; the shielding rate of gamma rays is 49.75% ( ¹³⁷ Cs source) and 34.25% ( ⁶⁰ Co source); the shielding rate of neutrons is as high as 92.73%; when the content of Pb and B is lower than that of existing shielding materials, the shielding effect of the Pb-B lead-based ray/neutron shielding composite material per unit mass is better than that of Pb/ B ₄ C composite material and boron-containing stainless steel, and comparable to lead-boron polyethylene. Realize the shielding function-mechanical structure integration of lead-magnesium-aluminum-boron or boride lead-based ray/neutron shielding materials. While improving the shielding performance, the shielding facility can be simplified and lightened.

Description of drawings

Fig. 1 is a scanning electron micrograph of the microstructure of the lead-magnesium-aluminum-boron lead-based ray/neutron shielding material of the present invention.

Fig. 2 is a scanning electron micrograph of the microstructure of the lead-magnesium-aluminum-boride lead-based ray/neutron shielding material of the present invention.

Detailed ways

Example 1: Add 49% of Pb, 39.2% of Mg and 9.8% of Al in the melting furnace, and then add 2.0% of boron. At this time, the mass percentage of PbMgAl lead-based alloy in the entire shielding material is 98%; B is 2%; the mass percentage of each component in the PbMgAl alloy is: Pb 50%, Mg 40%, Al 10%. Stir for 2 to 5 minutes to fully react and form each component, and let it stand for 2 to 3 minutes. The high-strength lead-magnesium-aluminum-boron lead-based ray/neutron shielding material is prepared by casting. The test results are as follows:

① Microstructure characteristics: After the surface treatment of the sample (grinding→polishing→corrosion), the scanning electron microscope (model XL30ESEM-TMP) was used to observe and analyze the microstructure characteristics of the sample, as shown in Figure 1. The test shows that the distribution of the alloy structure is uniform, and the interface between the B-containing phase and the Pb-containing phase is in good condition.

②Tensile strength test: Prepare the test sample bar and carry out the tensile strength test on the tensile mechanical testing machine. The test results show that the tensile strength of the high-strength lead-magnesium-aluminum-boron lead-based ray/neutron shielding material reaches 120MPa, which is 3 to 12 times that of Pb/B ₄ C composite material and lead-boron polyethylene, see Table 1. The elongation was 6.87%.

③Brinell hardness test: The Brinell hardness of the shielding material was measured on the HB-3000 Brinell hardness tester. The test results showed that the Brinell hardness of the high-strength lead-magnesium-aluminum-boron lead-based ray/neutron shielding material was 165, which is 8 to 40 times that of Pb/B ₄ C composite material and lead-boron polyethylene, see Table 1.

④ Shielding performance test: MG452 X-ray system is used for X-ray shielding performance test, and the X-ray energy is 65keV, 118keV and 250keV respectively. The gamma-ray shielding performance was tested using the gamma-ray exposure standard device, and the radiation sources were ¹³⁷ Cs (ray energy 661KeV) and ⁶⁰ Co (ray energy 1.25MeV). The neutron shielding experiment is detected by PTW-UNIDOS ionization chamber standard dosimeter and Am-Be neutron source moderation experiment device. Table 2 shows that high-strength lead-magnesium-aluminum-boron lead-based ray/neutron shielding materials have shielding rates of 97.9%, 99.22% and 90.29% for X-rays with energies of 65KeV, 118KeV and 250KeV, effectively solving the problem of energy mediation. The problem of "weak absorption region of Pb" between 40 and 88KeV; the shielding rate of gamma rays is 49.75% ( ¹³⁷ Cs source) and 34.25% ( ⁶⁰ Co source); the shielding rate of neutrons is as high as 92.73%. Table 3 shows that the shielding effect of the lead-magnesium-aluminum-boron lead-based ray/neutron shielding material per unit mass is better than that of pure lead and Pb/B ₄ C composite when the content of Pb and B is lower than that of the existing shielding materials material, and comparable to lead-boron polyethylene.

Embodiment 2: Add 50% of Pb, 35% of Mg and 10% of Al in the melting furnace, and then add 5.0% of boride. At this time, the mass percentage of PbMgAl lead-based alloy in the entire shielding material is 95%; the boride is 5%; the mass percentage of each component in the PbMgAl alloy is: Pb 52.6%, Mg 36.8%, Al 10.5%. Stir for 2 to 5 minutes to fully react and form each component, and let it stand for 2 to 3 minutes. The high-strength lead-magnesium-aluminum-boride lead-based ray/neutron shielding material is prepared by casting. The test results are as follows:

① Microstructure characteristics: After surface treatment of the sample (grinding→polishing→corrosion), the scanning electron microscope (model XL30ESEM-TMP) was used to observe and analyze the microstructure characteristics of the sample, as shown in Figure 2. The test shows that the distribution of the alloy structure is uniform, and the interfacial bonding of each phase is in good condition.

②Tensile strength test: Prepare a test sample bar and carry out the tensile strength test on the tensile mechanical testing machine. The test results show that the tensile strength of the high-strength lead-magnesium-aluminum-boride lead-based ray/neutron shielding material is Reach 105MPa, see Table 1. The elongation was 3.19%.

③Brinell hardness test: The Brinell hardness of the shielding material was measured on the HB-3000 Brinell hardness tester, and the test results showed that: the Brinell hardness of the high-strength lead-magnesium-aluminum-boride lead-based ray/neutron shielding material is 140, see Table 1.

④ Shielding performance test: MG452 X-ray system is used for X-ray shielding performance test, and the X-ray energy is 65keV, 118keV and 250keV respectively. The gamma-ray shielding performance was tested using the gamma-ray exposure standard device, and the radiation sources were ¹³⁷ Cs (ray energy 661KeV) and ⁶⁰ Co (ray energy 1.25MeV). The neutron shielding experiment is detected by PTW-UNIDOS ionization chamber standard dosimeter and Am-Be neutron source moderation experiment device. Table 2 shows that the high-strength lead-magnesium-aluminum-boride lead-based ray/neutron shielding material is 97.86%, 99.17% and 89.47% for the X-ray shielding rate of 65KeV, 118KeV and 250KeV, effectively solving the problem of energy Between 40 and 88KeV, the "weak absorption region of Pb"problem; the shielding rate of gamma rays is 46.81% (137Cs source) and 31.97% (60Co source); the neutron shielding rate reaches 89.5%. Table 3 shows that the lead-magnesium-aluminum-boride lead-based ray/neutron shielding material per unit mass has excellent shielding effect when the content of Pb and B is lower than that of the existing shielding materials.

Table 1 is a comparison table of tensile strength and Brinell hardness of the shielding material of the present invention.

Table 1

Material name Tensile strength (MPa) Brinell hardness Elongation (%) Lead-magnesium-aluminum-boron shielding material 120 165 6.87 Lead-magnesium-aluminum-boride shielding material 105 140 3.19 Pure Pb 10～20 4～9 - Pb-B polyethylene 10 3～4 - Pb/B ₄ C composite material 48.2 22.13 -

Table 2 is the shielding performance table of the shielding material of the present invention with a thickness of 20 mm.

Table 2

Table 3 is a comparison table of the shielding performance of the shielding material of the present invention with pure lead, Pb/B ₄ C composite material and lead-boron polyethylene with the same thickness.

table 3

Claims (3)

1. A high-strength lead-based material with comprehensive shielding effect of rays and neutrons is characterized in that: the shielding material is composed of PbMgAl lead-based alloy and boron or boride. 2. The high-strength lead-based material with comprehensive shielding effect of rays and neutrons according to claim 1, characterized in that: the mass percentage of the shielding material components is 0.3% to 10% of boron or boride, and the rest is lead base alloy. 3. The high-strength lead-based material with ray and neutron comprehensive shielding effect according to claim 2, characterized in that: the mass percent of each component in the PbMgAl lead-based alloy is Mg 10%～50%, Al 2%～ 20%, and the balance is Pb.

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