Multi-ray comprehensive shielding composite material design method

Abstract

The invention provides a multi-ray comprehensive shielding composite material design method. According to the invention, on the basis of a neutron and gamma ray shielding physical process, equivalent energy and equivalent intensity of three types of neutron rays and gamma rays in a radioactive source are calculated respectively, and the required amount of shielding components corresponding to each shielding step of each ray is calculated according to the equivalent energy and the equivalent intensity; and finally, arranging the component distribution of the multi-ray comprehensive shielding composite material according to the function of each shielding component. According to the method, the distribution of the shielding components in the matrix is regulated and controlled, so that the shielding components can participate in different rays and different shielding processes, and the thickness of the shielding material is reduced on the premise of ensuring good overall shielding performance of the material.

Description

Technical Field

[0001] The invention relates to the technical field of nuclear radiation shielding, and in particular to a design method for a multi-ray comprehensive shielding composite material. Background Art

[0002] The rapid development of nuclear technology has brought huge benefits to mankind, but it also has direct or indirect radiation hazards to the environment. Nuclear radiation mainly refers to neutron rays and gamma rays of various energies, which come from radioactive sources, natural environment and cosmic rays. As a special structural material, nuclear radiation shielding materials can be widely used in nuclear power plants, underwater and surface nuclear power plants, high-energy particle accelerators, spacecraft, nuclear medicine diagnosis and treatment equipment, and other fields.

[0003] The slowing down, absorption and shielding processes of different types of nuclear radiation require different components to achieve. When these shielding components are dispersed in the matrix material as particles, their distribution position has an important influence on the comprehensive shielding efficiency of the composite material. Combined with the current development trend of miniaturization and lightweight of various reactor components, the shielding layer needs to reduce the thickness of the material while ensuring good shielding performance. Therefore, how to reduce the thickness without losing shielding performance is a key issue in improving the applicability of nuclear radiation shielding materials. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a design method for a multi-ray comprehensive shielding composite material. Based on the physical process of neutron and gamma ray shielding, the present invention calculates the equivalent energy and equivalent intensity of three types of neutron rays and gamma rays in the radiation source respectively, and calculates the required amount of shielding components corresponding to each shielding step of each ray respectively based on them, and finally arranges the distribution of components of the multi-ray comprehensive shielding composite material according to the function of each shielding component. The present invention regulates the distribution of shielding components in the matrix through the above method, so that it can participate in different rays and different shielding processes, and reduces the thickness of the shielding material while ensuring the good overall shielding performance of the material.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] The present invention provides a method for designing a multi-ray comprehensive shielding composite material, wherein the multi-ray comprehensive shielding composite material comprises functional layers I to IV in sequence from the outside to the inside; the functional layers I to IV are composed of a matrix and shielding components doped in the matrix; the shielding components in the functional layers I to IV are selected from any one or more of shielding components (a) for absorbing gamma rays and heavy nuclear materials for slowing down high-energy neutrons, shielding components (b) for light nuclear materials for slowing down medium-energy neutrons, and shielding components (c) for absorbing low-energy neutrons;

[0007] The method comprises the following steps:

[0008] (1) Obtaining the equivalent energy and equivalent intensity of neutron rays in the radiation source; in the technical solution of the present invention, the neutron rays include high-energy neutron rays, medium-energy neutron rays and low-energy neutron rays; in certain specific embodiments, when writing a Monte Carlo calculation card in a simulation, the equivalent intensity of each neutron ray is represented by its ratio;

[0009] (2) Obtaining the total content of each shielding component, including:

[0010] Calculating the content of each shielding component required for the neutron rays in the radiation source during the first shielding action with the multi-ray comprehensive shielding composite material according to the equivalent energy and equivalent intensity of the neutron rays obtained in step (1)①; the first shielding action is the shielding action process between the initial neutron rays in the radiation source and the multi-ray comprehensive shielding composite material;

[0011] Obtaining the content of each shielding component required in the shielding process of the neutron ray after the first shielding through a genetic algorithm②;

[0012] The shielding component contents ① and ② obtained above are added to obtain the required total content of each shielding component;

[0013] (3) Arranging the hierarchical structure of the multi-ray comprehensive shielding composite material according to the total content of each shielding component calculated in step (2); the arranged hierarchical structure of the multi-ray comprehensive shielding composite material includes the type, content and layer thickness of the shielding components in each of the functional layers I to IV.

[0014] In the technical solution of the present invention, the substrate is a shielding substrate material commonly used in the art, specifically metals (stainless steel, aluminum alloy, etc.), polymers (polyethylene, epoxy resin, etc.), and concrete.

[0015] In the technical solution of the present invention, the shielding component (a) is selected from at least one of tungsten and lead; the shielding component (b) is selected from at least one of water, metal hydride and carbon; the shielding component (c) is preferably a material with a large thermal neutron absorption cross-section, such as at least one of gadolinium, boron / boron carbide, cadmium and samarium.

[0016] As a preferred implementation, the calculation formulas for the equivalent energy ē and equivalent intensity I of the neutron ray are shown in formula (1) and formula (2):

[0017]

[0018] I=∑I x (2)

[0019] In formula (1) and formula (2): E xis the energy of a neutron in the neutron energy spectrum of the neutron ray, in MeV; I x The energy in the neutron energy spectrum of the neutron ray is E x The intensity of neutrons, in n / s;

[0020] In the technical solution of the present invention, the equivalent energy of a certain neutron ray is the average energy of a neutron group in the neutron ray; the equivalent intensity of a certain neutron ray is the sum of the intensities of the neutrons in the neutron ray.

[0021] As a preferred embodiment, in step (2), the content of the shielding component ① is calculated according to formula (3):

[0022]

[0023] In formula (3), I is the equivalent intensity of the ray; I' is the intensity of the ray after shielding, and the neutron transmittance (I':I) is ≤50%;

[0024] σ t is the microscopic reaction cross section of the target nucleus;

[0025] N is the surface density of the target core, that is, the atomic density of the shielding component in the matrix; the volume fraction of the shielding component in the matrix of each functional layer is equivalent to the surface density of the target core, which is 5% to 15%;

[0026] x is the thickness;

[0027] The product of N and x is the content of the shielding component①;

[0028] In the technical solution of the present invention, the content of the required shielding component ① can be calculated by the physical theoretical model of the interaction between neutrons and target nuclei. After setting the neutron transmittance (I' / I*100%), the microscopic reaction cross section σ of the target nucleus is known. t That is, the total content of the target nucleus (shielding component) required can be calculated (Formula 3). Therefore, in the case of a known radiation source, the content of the shielding components required for each shielding process and the content of the shielding components specifically used for shielding secondary gamma rays and the thickness of each layer can be calculated according to Formula (3).

[0029] As a preferred embodiment, in step (3), the types of shielding components in each functional layer are as follows:

[0030] The functional layer I contains shielding components (a) to (c);

[0031] The functional layer II contains shielding components (a) to (c);

[0032] The functional layer III contains a shielding component (a) and a shielding component (c);

[0033] The functional layer IV contains a shielding component (a); in the technical solution of the present invention, the shielding component (c) releases secondary gamma rays when absorbing low-energy neutrons, so it is necessary to set the functional layer IV to absorb the secondary gamma rays.

[0034] As a preferred embodiment, in step (3), the shielding components in the functional layer I are tungsten, yttrium hydride and boron carbide; wherein tungsten is used to moderate initial high-energy neutrons; yttrium hydride is used to moderate initial medium-energy neutrons; and boron carbide is used to absorb initial low-energy neutrons.

[0035] As a preferred embodiment, in step (3), the shielding components in the functional layer II are yttrium hydride, boron carbide and tungsten; wherein yttrium hydride is used to slow down the medium-energy neutrons formed by the initial high-energy neutrons being slowed down once through the functional layer I; boron carbide is used to absorb the low-energy neutrons formed by the initial medium-energy neutrons being slowed down once through the functional layer I; and tungsten is used to shield the secondary gamma rays emitted by the initial low-energy neutrons during the absorption process of the functional layer I.

[0036] As a preferred embodiment, in step (3), the shielding components in the functional layer III are boron carbide and tungsten; wherein the boron carbide is used to absorb low-energy neutrons formed by secondary slowing down of initial high-energy neutrons by the functional layer II; and the tungsten is used to shield secondary gamma rays emitted by initial medium-energy neutrons during the absorption process of the functional layer II.

[0037] As a preferred embodiment, in step (3), the shielding component in the functional layer IV is tungsten; wherein tungsten is used to shield secondary gamma rays emitted during the absorption process of initial high-energy neutrons by the functional layer III.

[0038] As a preferred embodiment, in step (3), the arrangement of the content of the shielding component in each functional layer structure satisfies the following relationship:

[0039] ① The total content of any one of the shielding components in the multi-ray comprehensive shielding composite material is not less than the maximum value of the required content of the shielding component calculated in step (2), and is preferably equal to the maximum value of the required content of the shielding component calculated in step (2);

[0040] ② The shielding content of any one of the shielding components used to shield the neutron ray I in the radiation source is x, and the shielding content of any one of the shielding components used to shield the neutron ray II in the radiation source is y, and the energy range of the neutron ray I is higher than that of the neutron ray II; the content of the shielding component between two adjacent layers satisfies the following relationship:

[0041] ix≥y, the layer for shielding radiation I containing the shielding component is closer to the surface than the layer for shielding radiation II containing the shielding component, and the content of the shielding component in the layer for shielding radiation I containing the shielding component is ≤xy; the content of the shielding component in the layer for shielding radiation II containing the shielding component is ≥y;

[0042] or;

[0043] ii. x<y, the content of the shielding component in the layer for shielding radiation II containing the shielding component is ≥y; the layer adjacent to and close to the surface of the layer for shielding radiation II containing the shielding component does not contain the shielding component;

[0044] In the technical solution of the present invention, the above arrangement can avoid the components in each layer from repeatedly playing the shielding role, and achieve the thinning effect when the dosage ratio of each shielding component to the matrix of the multi-ray comprehensive shielding composite material is fixed.

[0045] Compared with the prior art, the present invention has the following advantages:

[0046] The present invention provides a method for designing a composite material for comprehensive shielding of multiple rays. Through different ray shielding physical processes and the order of occurrence of various shielding reactions, the distribution of multiple shielding components in the matrix material is regulated to achieve thinning of the shielding layer thickness while improving the shielding efficiency. The method provided by the present invention does not require screening a large number of samples one by one, but designs a shielding function component distribution scheme guided by the shielding physics principle, avoiding the problems of complicated experimental process and the like brought about by the large data sample screening method. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is a schematic diagram of the distribution of various shielding components and the multi-functions of each layer in Example 1 of the present invention.

[0048] Figure 2 Schematic diagram of thinning material by regulating the interlayer content of shielding components in Example 1 of the present invention.

[0049] Figure 3 This is a schematic diagram of the simulation comparison of the shielding efficiency of a single shielding component in a layer and multiple shielding components in a layer in Example 1 of the present invention. DETAILED DESCRIPTION

[0050] The following embodiments are only some embodiments of the present invention, rather than all embodiments. Therefore, the detailed description in the embodiments of the present invention provided below is not intended to limit the scope of the present invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work belong to the protection scope of the present invention.

[0051] In the present invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in the industry. The methods in the following embodiments are all conventional methods in the art unless otherwise specified.

[0052] Example 1

[0053] The present embodiment provides a method for designing a multi-ray integrated shielding composite material, wherein the multi-ray integrated shielding composite material includes functional layers I to IV in sequence from the outside to the inside; the functional layers I to IV are composed of a matrix (316L stainless steel in the present embodiment) and shielding components doped in the matrix; the shielding components are selected from any one or more of tungsten, yttrium hydride and boron carbide; wherein tungsten can undergo inelastic scattering with high-energy neutrons to slow them down into medium-energy neutrons, and can also absorb gamma rays; yttrium hydride can undergo elastic scattering with medium-energy neutrons to slow them down into low-energy neutrons; boron carbide can undergo absorption reaction with low-energy neutrons and release secondary gamma rays;

[0054] The method comprises the following steps:

[0055] 1) Setting the radiation source energy spectrum: The radiation source in this embodiment is a neutron point distribution energy spectrum, in which the energy of high-energy neutrons is 10 MeV and the energy of medium-energy neutrons is 10 -2 MeV, the energy of low-energy neutrons is 10 -5 MeV; the intensity ratio of the three types of neutron rays is: high energy neutron: medium energy neutron: low energy neutron = 1:1000:625000; since the shielding of gamma rays only requires one absorption process, the initial gamma rays in the radiation source are ignored in the actual operation case, and only neutron rays of different energy types are set;

[0056] 2) Calculate the total amount of shielding components required for each neutron ray based on the radiation source energy spectrum in step 1):

[0057] First, the neutron transmittance Since the intensities of the three neutron rays are different, the ratio of the neutron transmittance for the three rays is: high energy neutron: medium energy neutron: low energy neutron = 10000: 10: 0.016; if the shielding rate of high energy neutrons is 5E-1, then the shielding rate for medium energy neutrons is 5E-4, and for low energy neutrons is 8E-7. By looking up the relationship between the target nuclear reaction cross section and the neutron energy when the shielding component shields the corresponding rays, it can be obtained that the reaction cross section of tungsten for 10 MeV energy neutrons is about 0.2 barns, and the reaction cross section of medium energy neutrons for 10 -2 The cross section of the MeV neutron reaction is 6 barns, and the low-energy neutron reaction is 10 -5The reaction cross section of MeV neutrons is about 0 barns. According to formula (3), the product of the surface density N and the material thickness x is the atomic (target nucleus) mass of the shielding component. According to the shielding efficiency required for the three types of neutrons and the reaction cross section of the shielding component required for the first shielding reaction in this case, the ratio of the number of atoms of effective shielding elements in tungsten, yttrium hydride, and boron carbide is 15:5:6. Since the intensity of low-energy neutrons is much higher than that of medium-energy neutrons and high-energy neutrons, and the intensity of medium-energy neutrons is much higher than that of high-energy neutrons, the mass ratio of the above shielding materials is taken as the ratio of the total amount of each shielding material in the final material. That is, under the given radiation source intensity in this embodiment, there is no need to use a genetic algorithm to calculate the content of the corresponding shielding components required for subsequent reactions other than the first shielding reaction;

[0058]

[0059] 3) Layered arrangement of shielding components: The shielding components and their contents corresponding to the above-mentioned types of rays are designed. Figure 1 The distribution pattern shown is as follows: the first layer (i.e., the outermost layer) contains tungsten for slowing down the initial high-energy neutrons, yttrium hydride for slowing down the initial medium-energy neutrons, and boron carbide for absorbing the initial low-energy neutrons; the second layer contains yttrium hydride for slowing down the medium-energy neutrons formed by the initial high-energy neutrons, boron carbide for absorbing the low-energy neutrons formed by the initial medium-energy neutrons, and tungsten for shielding the secondary gamma rays emitted in the process of absorbing the initial low-energy neutrons; the third layer contains boron carbide responsible for absorbing the low-energy neutrons formed by the secondary slowing down of the initial high-energy neutrons, and responsible for shielding the gamma rays emitted by the initial medium-energy neutrons in the second layer absorption process; the fourth layer of materials is used to absorb the secondary gamma rays released when absorbing low-energy neutrons in the last step of the high-energy neutron shielding process;

[0060] Solutions with multiple shielding components per layer ( Figure 2 Right) and each layer contains a single shielding component ( Figure 2 In the left figure, the total content of each shielding component remains unchanged. Therefore, when a shielding component in a layer in the left figure is partially removed to other layers, the thickness of the layer where the shielding component originally resides can be reduced while ensuring that the mass percentage of the shielding component in the matrix remains unchanged ( Figure 2 The blue part of the right picture);

[0061] 4) Arrangement of shielding component content in each layer:

[0062] The total amount of each shielding material is roughly divided into Figure 2 In the distribution scheme shown in the right figure, and considering the subsequent manufacturability, the volume fraction of each shielding component in the matrix is ​​controlled to be 5% to 15%;

[0063] Four layers of materials are set in the ecard neutron transport simulation software based on Monte Carlo calculation. The ratio of the number of atoms of shielding components in the first layer of material is tungsten: hydrogen: boron: iron = 30:5:4:500; the ratio of the number of atoms of shielding components in the second layer is hydrogen: boron: tungsten: iron = 5:4:10:250; the ratio of the number of atoms of shielding components in the third layer is boron carbide: tungsten: iron = 2:5:180; the ratio of the number of atoms of shielding components in the fourth layer is tungsten: iron = 5:180, and the tungsten content is obtained by genetic algorithm; the material thickness is set to 10 mm for the first layer, 5 mm for the second layer, 3.3 mm for the third layer, and 3.3 mm for the fourth layer, and each layer is arranged tightly in order.

[0064] The total thickness of the nuclear shielding layer containing multiple shielding components obtained by the above arrangement in this embodiment is 21.6 mm.

[0065] This embodiment also sets up a control group in which each layer contains only one shielding component. The control group is four layers of nuclear shielding material of equal thickness with a total thickness of 40 mm. The ratio of the number of atoms of the shielding components in the first layer of material is tungsten: iron = 48:100; the ratio of the number of atoms of the shielding components in the second layer is hydrogen: iron = 4:100; the ratio of the number of atoms of the shielding components in the third layer is boron carbide: iron = 16:100; and the ratio of the number of atoms of the shielding components in the fourth layer is tungsten: iron = 48:100.

[0066] The simulation diagram of the shielding efficiency of the above two nuclear shielding materials set in this embodiment is shown in Figure 3 ,from Figure 3 It can be clearly seen from the visualization interface that the reflection and transmittance of neutrons are reduced, indicating that the neutron absorption rate is improved. The shielding design of multiple materials in each layer can better realize the functional and structural integration of the shielding layer than the shielding design of single material in each layer, and it is in line with the current development trend of miniaturization and lightweight of various reactors.

[0067] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for designing a multi-ray integrated shielding composite material, characterized in that: The multi-ray comprehensive shielding composite material comprises functional layers I to IV in order from the outside to the inside; the functional layers I to IV are composed of a matrix and shielding components doped in the matrix; the shielding components in the functional layers I to IV are selected from any one or more of shielding components (a) for absorbing gamma rays and heavy nuclear materials for slowing down high-energy neutrons, shielding components (b) for light nuclear materials for slowing down medium-energy neutrons, and shielding components (c) for absorbing low-energy neutrons; The method comprises the following steps: (1) obtaining the equivalent energy and equivalent intensity of neutron rays in the radiation source; in the technical solution of the present invention, the neutron rays include high-energy neutron rays, medium-energy neutron rays and low-energy neutron rays; = (2) Obtaining the total content of each shielding component, including: Calculating the content of each shielding component required for the neutron rays in the radiation source during the first shielding action with the multi-ray comprehensive shielding composite material according to the equivalent energy and equivalent intensity of the neutron rays obtained in step (1)①; the first shielding action is the shielding action process between the initial neutron rays in the radiation source and the multi-ray comprehensive shielding composite material; Obtaining the content of each shielding component required in the shielding process of the neutron ray after the first shielding through a genetic algorithm②; The shielding component contents ① and ② obtained above are added to obtain the required total content of each shielding component; (3) Arranging the hierarchical structure of the multi-ray comprehensive shielding composite material according to the total content of each shielding component calculated in step (2); the arranged hierarchical structure of the multi-ray comprehensive shielding composite material includes the type, content and layer thickness of the shielding components in each of the functional layers I to IV.

2. The method according to claim 1, characterized in that The matrix is ​​selected from any one of metal, polymer and concrete; Preferably, the shielding component (a) is selected from at least one of tungsten and lead; the shielding component (b) is selected from at least one of water, metal hydride and carbon; the shielding component (c) is selected from at least one of gadolinium, boron / boron carbide, cadmium and samarium.

3. The method according to claim 1, characterized in that In step (1), the equivalent energy of the neutron beam is The calculation formulas of the equivalent strength I are shown in formula (1) and formula (2): I=∑I x (2) In formula (1) and formula (2): E x is the energy of a neutron in the neutron energy spectrum of the neutron ray, in MeV; I x The energy in the neutron energy spectrum of the neutron ray is E x The intensity of neutrons, in n / s.

4. The method according to claim 1, characterized in that: In step (2), the content of the shielding component ① is calculated according to formula (3): In formula (3), I is the equivalent intensity of the ray; I' is the intensity of the ray after shielding, and the neutron transmittance (I':I) is ≤50%; σ t is the microscopic reaction cross section of the target nucleus; N is the surface density of the target core, which is 5% to 15%; x is the thickness; The product of N and x is the content of the shielding component①.

5. The method according to claim 1, characterized in that In step (3), the types of shielding components in each functional layer are as follows: The functional layer I contains shielding components (a) to (c); The functional layer II contains shielding components (a) to (c); The functional layer III contains a shielding component (a) and a shielding component (c); The functional layer IV contains a barrier component (a).

6. The method according to claim 5, characterized in that In step (3), the shielding components in the functional layer I are tungsten, yttrium hydride and boron carbide.

7. The method according to claim 5, characterized in that In step (3), the shielding components in the functional layer II are yttrium hydride, boron carbide and tungsten.

8. The method according to claim 5, characterized in that In step (3), the shielding components in the functional layer III are boron carbide and tungsten.

9. The method according to claim 5, characterized in that In step (3), the shielding component in the functional layer IV is tungsten.

10. The method according to any one of claims 1 to 9, characterized in that: In step (3), the arrangement of the content of the shielding component in each functional layer structure satisfies the following relationship: ① The total content of any one of the shielding components in the multi-ray comprehensive shielding composite material is not less than the maximum value of the required content of the shielding component calculated in step (2), and is preferably equal to the maximum value of the required content of the shielding component calculated in step (2); ② The shielding content of any one of the shielding components used to shield the neutron ray I in the radiation source is x, and the shielding content of any one of the shielding components used to shield the neutron ray II in the radiation source is y, and the energy range of the neutron ray I is higher than that of the neutron ray II; the content of the shielding component between two adjacent layers satisfies the following relationship: ix≥y, the layer for shielding radiation I containing the shielding component is closer to the surface than the layer for shielding radiation II containing the shielding component, and the content of the shielding component in the layer for shielding radiation I containing the shielding component is ≤xy; the content of the shielding component in the layer for shielding radiation II containing the shielding component is ≥y; or; ii. x<y, the content of the shielding component in the layer for shielding radiation II containing the shielding component is ≥y; the layer adjacent to and close to the surface of the layer for shielding radiation II containing the shielding component does not contain the shielding component.

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