Inorganic anti-neutron shielding material and preparation method thereof

Abstract

The embodiment of the invention discloses an inorganic anti-neutron shielding material and a preparation method thereof. The inorganic anti-neutron shielding material comprises the following raw materials in percentage by weight: 5-60% of a base material; 1-90% of lightweight aggregate; 1-20% of a neutron shielding functional auxiliary agent; and 4-40% of water. The inorganic hydroxide is used as the lightweight aggregate, so that the density of the filling aggregate is greatly reduced, the overall weight of the shielding material is reduced, and meanwhile, the phenomenon that the aggregate sinks when separated from cement due to the fact that the gravity is too concentrated due to the too large specific gravity of the aggregate is avoided. In addition, the inorganic anti-neutron shielding material provided by the invention has good neutron shielding performance and mechanical properties. The invention can further enrich the variety and application range of the shielding material, and has important strategic significance and positive social significance.

Description

Technical Field

[0001] This invention relates to the field of shielding materials technology, specifically to an inorganic neutron shielding material and its preparation method. Background Technology

[0002] The development and application of nuclear technology has promoted the development of many fields such as nuclear power, national defense, scientific research, agriculture, and medicine. However, its safety has always been a major concern. The large amount of radiation produced by nuclear reactions, such as alpha, beta, gamma, X-rays and neutrons, can induce a variety of diseases and gene mutations, posing a great potential threat to human health and causing long-term damage to the natural environment that is difficult to repair.

[0003] Neutrons are composed of neutral particles without electric charge and possess extremely high penetrating power. Based on energy, they can be classified into fast neutrons, intermediate-speed neutrons, and slow neutrons. The harm they cause to the human body is more severe than that caused by the same dose of gamma rays or X-rays. Neutron shielding cannot be effectively achieved simply by increasing the thickness of protective materials; it is a key focus of current radiation protection research. For fast and intermediate-speed neutrons, protection requires not only heavy elements but also as many light elements as possible, ideally containing a high proportion of hydrogen atoms, such as hydrogen-rich substances like water and paraffin. For slow neutrons, materials capable of absorbing or shielding them are needed.

[0004] Currently, commonly used composite shielding materials are mainly boron-containing polyethylene, lead-boron polyethylene, and lithium-containing polyethylene. These materials have a much lower specific gravity than steel and their manufacturing processes are mature. However, their temperature resistance is not high, with long-term operating temperatures not exceeding 80°C, limiting their use as reactor shielding materials to low-temperature areas. Generally speaking, inorganic materials have better temperature resistance than organic polymers, possess good structural strength, and are easily incorporated with other functional materials, making them feasible for research.

[0005] The most widely used inorganic shielding material is cement concrete, which has advantages such as abundant raw material sources, ease of construction, and good plasticity, and provides a certain shielding effect against neutrons and gamma rays. However, the shielding efficiency of cement alone is relatively low. A common approach is to add heavy aggregates such as barite, magnetite, and limonite to the cement, while introducing sufficient water of crystallization and boron-containing neutron absorbers to improve the neutron shielding effect. However, this method often results in segregation and poor uniformity of the concrete due to the high density of the added aggregates, and it does not meet the current design principles of lightweight and miniaturized shielding materials. Furthermore, from a practical application perspective, with increased usage time or rising ambient temperatures (generally above 80℃), the bound water contained in the cement hydration gradually decreases, reducing the hydrogen content in the material and affecting neutron shielding performance. On the other hand, rising temperatures can cause expansion within the cement matrix, potentially leading to cracks and impacting the material's mechanical properties and service life. These factors hinder the promotion and application of radiation-shielding concrete. Summary of the Invention

[0006] To address the existing technical problems, it is necessary to propose a suitable inorganic lightweight aggregate that exhibits stable properties at high temperatures, good dispersibility with cementitious materials, and a relatively high hydrogen content. This ensures that the concrete shielding material possesses stable neutron shielding performance, good homogeneity, and mechanical strength, meeting the requirements of radiation-shielding concrete in high-temperature service environments. Furthermore, based on the material's composition system, molding process research should be conducted to ensure its operability and applicability.

[0007] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions:

[0008] According to a first aspect of the present invention, the present invention provides an inorganic neutron shielding material, the inorganic neutron shielding material comprising, by weight percentage, the following raw materials:

[0009] Matrix material: 5-60%;

[0010] Lightweight aggregate: 1-90%;

[0011] Neutron shielding additive: 1-20%;

[0012] Water: 4-40%.

[0013] Furthermore, the matrix material is selected from one or more of silicate cement, aluminate cement, sulfoaluminate cement, ferroaluminate cement, fluoroaluminate cement, phosphate cement, and sulfate-resistant silicate cement.

[0014] Furthermore, the lightweight aggregate is selected from one or more of magnesium hydroxide, aluminum hydroxide, and calcium hydroxide.

[0015] Furthermore, the neutron shielding functional additive is selected from one or more of boron carbide, boron oxide, boron nitride, lithium fluoride, and lithium carbonate.

[0016] Furthermore, the inorganic neutron shielding material comprises the following raw materials by weight percentage:

[0017] Sulfate-resistant silicate cement: 15-55%;

[0018] Magnesium hydroxide 10-70%;

[0019] Boron carbide 1-5%;

[0020] Water content: 10-35%.

[0021] According to a second aspect of the present invention, the present invention provides a method for preparing an inorganic neutron shielding material as described in any of the preceding claims, the method comprising the following steps:

[0022] (1) Dry powder mixing: The weighed matrix material, lightweight aggregate and neutron shielding functional additive are put into a high-speed mixer and mixed evenly to obtain a dry powder mixture;

[0023] (2) Wet powder mixing: slowly pour water into the middle of the dry powder mixture and mix evenly to obtain a wet powder mixture;

[0024] (3) Compression molding: The wet powder mixture is put into a molding die for compression molding to obtain the compression molded product;

[0025] (4) Heat treatment: The molded product is placed in an oven for heat treatment to obtain the inorganic neutron shielding material.

[0026] Furthermore, in step (1), the material is mixed by alternating speeds. First, it is mixed at a speed of 300-500 rpm for 10-30 seconds, then switched to a speed of 1000-1500 rpm for 5-20 seconds, then stopped, and then mixed again at a speed of low to high. This process is repeated 2-5 times.

[0027] Furthermore, in step (2), the mixing is carried out by alternating speeds. First, the mixing is started at a speed of 200-400 rpm for 5-15 seconds, then switched to a speed of 700-1000 rpm for 3-10 seconds, and then stopped. The mixing is then carried out by alternating low speed and high speed. This process is repeated 2-5 times. During the mixing process, the material temperature should be monitored to be below 50°C.

[0028] Further, in step (3), the molding conditions are: mold temperature 20-50℃, initial molding pressure 3-6MPa, final molding pressure 10-20MPa, and holding pressure 4-6h.

[0029] Further, in step (4), the conditions for the heat treatment are: oven temperature set at 80-110°C, and treatment time at 4-10h.

[0030] The embodiments of the present invention have the following advantages:

[0031] This invention provides an inorganic neutron shielding material and its preparation method. Inorganic hydroxide is used as a lightweight aggregate to replace traditional barite coarse aggregate, significantly reducing the density of the filler aggregate and thus the overall weight of the shielding material. Simultaneously, it avoids the "sinking" phenomenon caused by excessive aggregate density leading to excessive gravity concentration and separation from the cement. Inorganic hydroxide has a relatively high hydrogen content and remains stable at high temperatures, ensuring good neutron shielding performance. Furthermore, based on the material's formulation system, molding and heat treatment processes were developed to improve the product's performance. Therefore, the research and development of this material can further enrich the types and applications of shielding materials, possessing significant strategic and positive social significance. Attached Figure Description

[0032] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0033] Figure 1 This is a sample of an inorganic neutron shielding material provided by the present invention;

[0034] Figure 2 This is a processing diagram of the test strip provided by the present invention. Detailed Implementation

[0035] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Example 1

[0037] This embodiment provides an inorganic neutron shielding material, the raw materials of which are: 42.5-16.5 parts silicate cement C, 70 parts magnesium hydroxide, 2 parts boron carbide, and 11.5 parts water.

[0038] The preparation method of the above-mentioned inorganic neutron shielding material is as follows:

[0039] (1) Dry powder mixing: Mix at 500 rpm for 15 seconds, then switch to 1500 rpm for 10 seconds, stop for 5 seconds, then mix at 500 rpm for 15 seconds, then switch to 1500 rpm for 5 seconds, stop for 5 seconds, then mix at 500 rpm for 10 seconds, then switch to 1500 rpm for 5 seconds.

[0040] (2) Wet powder mixing: Mix at 300 rpm for 10 seconds, then switch to 1000 rpm for 5 seconds, stop for 5 seconds, then mix at 300 rpm for 10 seconds, then switch to 1000 rpm for 5 seconds, stop for 5 seconds, then mix at 300 rpm for 10 seconds, then switch to 1000 rpm for 5 seconds.

[0041] (3) Compression molding: The mold temperature is 35℃, the initial molding pressure is 3MPa, the final molding pressure is 16MPa, and the product is removed after maintaining the pressure for 6 hours.

[0042] (4) Heat treatment: The oven temperature is set to 90℃ and the treatment time is 8h.

[0043] Example 2

[0044] This embodiment provides an inorganic neutron shielding material, which differs from Embodiment 1 only in that an equal amount of aluminate cement C50 is used instead of silicate cement C42.5. Specifically, the raw materials for this embodiment are: 16.5 parts aluminate cement C50, 70 parts magnesium hydroxide, 2 parts boron carbide, and 11.5 parts water.

[0045] Example 3

[0046] This embodiment provides an inorganic neutron shielding material, which differs from Embodiment 1 only in that an equal amount of sulfate-resistant silicate cement PHSR 42.5 is used instead of silicate cement C42.5. Specifically, the raw materials for this embodiment are: 16.5 parts sulfate-resistant silicate cement PHSR 42.5, 70 parts magnesium hydroxide, 2 parts boron carbide, and 11.5 parts water.

[0047] Detection of density and hydrogen content

[0048] Density: The density was calculated by weighing the sample before and after heat treatment, and then dividing the weight by the sample volume to obtain the density before and after heat treatment.

[0049] Hydrogen content: The hydrogen content of each component is calculated from its molecular formula. Then, the hydrogen content of the sample before heat treatment is calculated from the ratio of the components. The weight change before and after heat treatment is considered as the loss of water inside the sample, while the contents of other components remain unchanged. The hydrogen content of the sample after heat treatment can be calculated using the same method.

[0050] The test results of Examples 1-3 are shown in Table 1 below.

[0051] Table 1

[0052] index Example 1 Example 2 Example 3 initial density 1.806 1.804 2.025 Heat treatment density 1.634 1.636 1.852 Initial hydrogen content per unit volume (theoretical value) 0.0667 0.0666 0.0748 Hydrogen content per unit volume after heat treatment (theoretical value) 0.0476 0.0480 0.0555

[0053] The hydrogen content in a material determines its fast neutron shielding performance. As shown in Table 1, the sample in Example 3 has the highest hydrogen content, indicating that the sulfate-resistant silicate cement has a better chemically bound water content.

[0054] Example 4

[0055] This embodiment provides an inorganic neutron shielding material, the raw materials of which are: 2.523 parts of sulfate-resistant silicate cement P HSR4, 60 parts of magnesium hydroxide, 2 parts of magnesium hydroxide, and 15 parts of water.

[0056] The preparation method of the inorganic neutron shielding material in this embodiment is the same as in Embodiment 1.

[0057] Example 5

[0058] This embodiment provides an inorganic neutron shielding material, the raw materials of which are: 2.535 parts of sulfate-resistant silicate cement P HSR4, 40 parts of magnesium hydroxide, 2 parts of boron carbide, and 23 parts of water.

[0059] The preparation method of the inorganic neutron shielding material in this embodiment is the same as in Embodiment 1.

[0060] Example 6

[0061] This embodiment provides an inorganic neutron shielding material, the raw materials of which are: 2.553 parts of sulfate-resistant silicate cement P HSR4, 10 parts of magnesium hydroxide, 2 parts of boron carbide, and 35 parts of water.

[0062] The preparation method of the inorganic neutron shielding material in this embodiment is the same as in Embodiment 1.

[0063] Density: Five samples were prepared for each example using the weighing method, and the average value was taken.

[0064] Density uniformity: the difference between the maximum and minimum density values ​​of the five samples.

[0065] Bending strength: The test shall be conducted in accordance with the standard GB / T2567-2008 Test Method for Performance of Resin Castings, with a test speed of 10 mm / min.

[0066] Compressive strength and compressive modulus: The test shall be conducted in accordance with the standard GB / T2567-2008 Test Method for Properties of Resin Castings, with a test speed of 5 mm / min.

[0067] Fast neutron shielding efficiency: The standard is Q / CYSXY0009-2022 "Determination of Attenuation Performance of Neutron Shielding Materials".

[0068] The test results of Examples 3-6 are shown in Table 2 below.

[0069] Table 2

[0070]

[0071] The horizontal direction of the template refers to the direction perpendicular to the pressure applied during molding, while the thickness direction of the template refers to the direction parallel to the pressure applied during molding. Examining the mechanical properties in both directions provides a more comprehensive understanding of the internal structure of the material.

[0072] Table 2 shows that the density of the upper and lower layers of the sample is highly consistent and uniform, indicating a homogeneous internal structure and reasonable molding process parameters. The mechanical property data from Examples 3-6 show that increasing the amount of magnesium hydroxide added can improve the mechanical strength of concrete materials within a certain range; however, exceeding a certain proportion negatively impacts mechanical properties. This is mainly because magnesium hydroxide is an alkaline inorganic compound that partially ionizes into OH groups upon contact with water. - The ions provide an alkaline environment for the reaction, which is beneficial to the hydration reaction of cement. Unreacted magnesium hydroxide acts as an inert aggregate in the cement gel, increasing the material's density and thus improving its mechanical strength. However, when the amount of magnesium hydroxide added is too high, the continuous phase of the cement gel inside the material is broken, creating weak points at the interface between the two substances. When the material is subjected to external forces, these weak points will fracture first, thus reducing the material's mechanical properties. Example 4 achieves a good balance between shielding performance and mechanical properties, resulting in the best overall performance.

[0073] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. An inorganic neutron shielding material, characterized in that, The inorganic neutron shielding material comprises the following raw materials by weight percentage: Matrix material: 5-60%; Lightweight aggregate: 1-90%; Neutron shielding additive: 1-20%; Water: 4-40%.

2. The inorganic neutron shielding material according to claim 1, characterized in that, The matrix material is selected from one or more of silicate cement, aluminate cement, sulfoaluminate cement, ferroaluminate cement, fluoroaluminate cement, phosphate cement, and sulfate-resistant silicate cement.

3. The inorganic neutron shielding material according to claim 1, characterized in that, The lightweight aggregate is selected from one or more of magnesium hydroxide, aluminum hydroxide, and calcium hydroxide.

4. The inorganic neutron shielding material according to claim 1, characterized in that, The neutron shielding functional additive is selected from one or more of boron carbide, boron oxide, boron nitride, lithium fluoride, and lithium carbonate.

5. The inorganic neutron shielding material according to claim 1, characterized in that, The inorganic neutron shielding material comprises the following raw materials by weight percentage: Sulfate-resistant silicate cement: 15-55%; Magnesium hydroxide 10-70%; Boron carbide 1-5%; Water content: 10-35%.

6. The method for preparing the inorganic neutron shielding material according to any one of claims 1-5, characterized in that, The method includes the following steps: (1) Dry powder mixing: The weighed matrix material, lightweight aggregate and neutron shielding functional additive are put into a high-speed mixer and mixed evenly to obtain a dry powder mixture; (2) Wet powder mixing: slowly pour water into the middle of the dry powder mixture and mix evenly to obtain a wet powder mixture; (3) Compression molding: The wet powder mixture is put into a molding die for compression molding to obtain the compression molded product; (4) Heat treatment: The molded product is placed in an oven for heat treatment to obtain the inorganic neutron shielding material.

7. The method for preparing the inorganic neutron shielding material according to claim 6, characterized in that, In step (1), The material is mixed by alternating speeds. First, mix at 300-500 rpm for 10-30 seconds, then switch to 1000-1500 rpm for 5-20 seconds. After that, stop the machine and mix again at low speed to high speed. Repeat this mixing process 2-5 times.

8. The method for preparing the inorganic neutron shielding material according to claim 6, characterized in that, In step (2), Mixing is performed using a variable speed alternation method. First, start mixing at a speed of 200-400 rpm for 5-15 seconds, then switch to a speed of 700-1000 rpm for 3-10 seconds, then stop the machine, and then mix again at a speed of low to high. Repeat this mixing process 2-5 times. During the mixing process, the material temperature should be monitored to be below 50℃.

9. The method for preparing the inorganic neutron shielding material according to claim 6, characterized in that, In step (3), The molding conditions are as follows: mold temperature 20-50℃, initial molding pressure 3-6MPa, final molding pressure 10-20MPa, and holding pressure for 4-6 hours.

10. The method for preparing the inorganic neutron shielding material according to claim 6, characterized in that, In step (4), The heat treatment conditions are: oven temperature set at 80-110℃, treatment time at 4-10h.

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