A high-temperature-resistant metal hydride-based composite shielding material and a preparation method thereof

Abstract

The application discloses a high-temperature-resistant composite shielding material based on metal hydride and a preparation method thereof, relates to the technical field of nuclear materials, and is composed of rare earth metal hydride and tungsten boride material; the mass percentage of tungsten boride is 1-70%, and the mass percentage of rare earth hydride is 30-99%. The high-temperature-resistant composite shielding material is prepared by using a hot isostatic pressing sintering method or a hot pressing sintering method; the hot isostatic pressing sintering method is used for the preparation of a large-size high-temperature-resistant composite shielding material, and the hot pressing sintering method is used for the preparation of a small-size spliced shielding plate. The prepared high-temperature-resistant composite shielding material can be used at a temperature of above 800 DEG C for a long time, has high hydrogen content, has good neutron gamma comprehensive shielding performance, can be used on the inner side of a heat preservation layer, can significantly reduce the weight and volume of a shielding body, and thus improves the flexibility of a small reactor.

Description

Technical Field

[0001] This invention relates to the field of nuclear materials technology, specifically to a high-temperature resistant composite shielding material based on metal hydrides and its preparation method. Background Technology

[0002] To increase the power density of reactors, the design operating temperature of reactors is becoming increasingly higher. Small reactors place higher demands on the operating temperature and shielding efficiency of shielding materials, with some reactors operating at temperatures exceeding 800℃. The shield is a crucial component of the reactor, and its weight and volume directly affect the reactor's flexibility. Therefore, reactors require shields to be as lightweight and compact as possible.

[0003] The radiation sources of a reactor include fast neutrons and gamma rays. Fast neutrons generally need to be moderated by hydrogen-containing materials before being absorbed by elements with high neutron absorption cross-sections. Currently, neutron moderation materials mainly include water, polyethylene, epoxy resin, and silicone resin, but these materials have low operating temperatures. Organic materials are prone to decomposition at high temperatures; for example, the operating temperature of polyethylene-based shielding materials generally does not exceed 120°C, and epoxy resin does not exceed 160°C. Gamma rays are generally shielded using high-density materials, commonly including lead and lead-boron polyethylene, but lead-boron polyethylene has a lower operating temperature, generally not exceeding 120°C, and is currently the most widely used composite shielding material. Summary of the Invention

[0004] Given the current limitations of shielding materials, such as low operating temperature and insufficient shielding efficiency, which fail to meet the material selection requirements for neutron shielding design in small reactors, the present invention aims to provide a high-temperature resistant composite shielding material based on metal hydrides and its preparation method. This material has a long-term operating temperature exceeding 800℃, a high hydrogen content, and good overall neutron and gamma shielding performance. It can be used on the inner side of the insulation layer, significantly reducing the weight and volume of the shield, thereby improving the flexibility of small reactors.

[0005] This invention is achieved through the following technical solution:

[0006] In a first aspect, this application provides a high-temperature resistant composite shielding material based on metal hydrides, the high-temperature resistant composite shielding material being composed of rare earth metal hydrides and tungsten boride; the tungsten boride material having a mass percentage of 1% to 70%, and the rare earth hydrides having a mass percentage of 30% to 99%.

[0007] Rare earth metal hydrides primarily provide hydrogen for high-temperature shielding materials and ensure the stability of hydrogen at high temperatures. Boron in tungsten boride mainly absorbs moderated thermal neutrons. Boron has a large absorption cross-section for medium- and low-energy neutrons and low secondary gamma shielding energy. Tungsten boride has a high tungsten atomic coefficient, resulting in a high fast neutron scattering cross-section and gamma shielding efficiency, providing high shielding efficiency for both fast neutrons and secondary gamma rays. When fast neutrons are incident on the shielding material, tungsten atoms first scatter and moderate them, then the hydrogen atoms in the rare earth metal hydrides further moderate them, and finally, the boron atoms absorb the neutrons, thus shielding them. Additionally, the secondary gamma rays generated after the boron atoms absorb the neutrons are absorbed by the tungsten atoms.

[0008] In addition, the inventors discovered in experiments that rare earth hydrides have good sinterability, while tungsten boride has a high melting point and is extremely difficult to sinter. As a binder phase, rare earth hydrides can be used to prepare composite materials in which tungsten boride is dispersed in rare earth hydrides at a lower temperature. Moreover, tungsten boride and rare earth metal hydride components have good compatibility at the sintering temperature of the composite material and do not undergo interfacial reactions. Therefore, composite materials in which tungsten boride is dispersed in rare earth hydrides can be prepared by powder metallurgy.

[0009] This invention significantly improves the thermal neutron shielding capability of rare earth metal hydrides by adding a small amount of tungsten boride. The amount of tungsten boride added to the composite material should not be less than 1%. The density of the material increases significantly with the increase of tungsten boride addition, and the shielding capability against gamma rays increases. However, with the increase of tungsten boride, tungsten boride, as a second phase, hinders the sintering densification of the composite material, thus affecting the density of the material. In addition, with the increase of tungsten boride, the neutron moderator component decreases, affecting the shielding efficiency of the shielding material against fast neutrons. Therefore, the tungsten boride content should not exceed 70%.

[0010] Lead-boron polyethylene (BOPE) is currently the shielding material with the best overall shielding performance and has been widely used in nuclear power plant reactors, research reactors, and reprocessing plants. The high-temperature resistant shielding material in this invention has superior neutron shielding performance, gamma shielding performance, and high-temperature shielding performance compared to the in-service BOPE material. Replacing BOPE with the high-temperature resistant composite shielding material in this invention in small reactors can significantly reduce the weight and volume of the shielding body.

[0011] In one specific embodiment, the rare earth metal hydride includes any one or a mixture of two of the following components: yttrium hydride, gadolinium hydride, cerium hydride, and lanthanum hydride.

[0012] In one specific embodiment, the tungsten boride material includes any one or a mixture of two of the following components: tungsten monoboride, tungsten diboride, tungsten pentaboride, and tungsten diboride.

[0013] Secondly, this application provides a method for preparing a high-temperature resistant composite shielding material based on metal hydrides, including preparation by hot isostatic pressing (HIP) or hot pressing (HT) sintering; the HIP method is used for the preparation of large-size high-temperature resistant composite shielding materials, and the HT method is used for the preparation of small-size spliced ​​shielding plates.

[0014] In a specific embodiment, the preparation of large-size high-temperature resistant composite shielding material using the hot isostatic pressing sintering method includes the following steps:

[0015] Preparation of rare earth hydride powder: Rare earth metals are placed in a high-vacuum heating furnace, evacuated, and heated. After the temperature inside the furnace stabilizes, hydrogen gas is introduced to allow the rare earth metals to fully permeate with hydrogen. After holding at the temperature, the furnace is cooled down to obtain rare earth metal hydrides. The introduced hydrogen gas is high-purity hydrogen, and the furnace pressure is maintained slightly above 1 atm for 1–4 hours.

[0016] In one specific implementation, the vacuum is evacuated to 10... -4 Pa~10 -2 Pa.

[0017] In one specific embodiment, after vacuuming, the temperature is raised to 700℃~900℃. The holding time is 10~90 minutes.

[0018] Mixing: Place rare earth hydride powder and tungsten boride powder into a mixer and mix evenly according to the proportion;

[0019] Assembly: Place the mixed powder into a stainless steel sleeve and compact it, cover it with a cover plate with an exhaust pipe, and weld the cover plate to the sleeve;

[0020] Exhaust and vacuum sealing: The pre-welded casing is connected to the vacuum exhaust station. After evacuation, the casing is heated, and then the exhaust pipe is sealed to maintain a high vacuum inside the casing; specifically, evacuation to 10... -2 Pa~1Pa, the temperature during heat treatment is controlled at 300℃~500℃, the holding time is 1~5 hours, until the vacuum degree is better than 1Pa, and the exhaust pipe is immediately sealed.

[0021] Hot isostatic pressing (HIP): The sizing and vacuum-sealed sizing jacket is placed into a hot isostatic pressing furnace for hot isostatic pressing.

[0022] Remove the sheath and surface finish: After removing the sheath by machining, a high-temperature resistant composite shielding material is obtained.

[0023] In one specific embodiment, during mixing, rubber balls are loaded into the mixer, the rotation speed is controlled at 30~90 rpm, and the mixing time is controlled at 30~60 minutes.

[0024] In one specific embodiment, during assembly, the powder packing density is made to reach 55% to 65%.

[0025] In one specific embodiment, the pressure is controlled at 100MPa~200MPa during hot isostatic pressing.

[0026] In one specific embodiment, the temperature during hot isostatic pressing is controlled at 800℃~1000℃, the holding time is controlled at 30~90 minutes, and after the holding and pressing are completed, the temperature is reduced to below 700℃ before depressurization.

[0027] The hot isostatic pressing (HIP) method for the composite shielding material in this invention differs from the HIP treatment of other materials. Generally, the HIP treatment of materials requires the complete removal of all gases from the cladding, and the vacuum level is typically better than 10. -2 Pa, with a processing temperature above 800℃, is used to fully remove the gas adsorbed by the powder and avoid bulging during hot isostatic pressing sintering. The preparation method in this invention releases hydrogen gas during high-temperature sintering. Under high pressure, the hydrogen released by the rare earth hydrides is reabsorbed by the hydrides. Utilizing the principle that the external pressure is greater than the internal gas pressure of the casing, the composite shielding material is densified. Hot isostatic pressing sintering needs to be performed at high pressure and relatively low temperature. Therefore, the sintering temperature of the rare earth metal hydrides should not be too high, and pressure needs to be continued during the cooling process. The temperature needs to be lowered to below 700℃ before depressurization to ensure that the shielding material inside the casing is in a high hydrogen partial pressure state. Otherwise, according to conventional hot isostatic pressing methods, if the pressure is immediately reduced after the heat treatment, the material will bulge and break.

[0028] In a specific embodiment, the hot-pressing sintering method for small-sized spliced ​​shielding plates includes the following steps:

[0029] Preparation of rare earth hydride powder: Rare earth metal is placed in a high vacuum heating furnace, vacuumed and heated. After the temperature in the heating furnace stabilizes, hydrogen is introduced to allow the rare earth metal to fully permeate with hydrogen. After holding at the temperature, it is cooled down with the furnace and then crushed to obtain rare earth metal hydride powder.

[0030] Mixing: Place rare earth hydride powder and tungsten boride powder into a mixer and mix evenly according to the proportion; pour the mixed powder into a graphite or silicon carbide mold and compact it;

[0031] Hot pressing sintering: The mold containing powder is placed into a hot press furnace, high-purity argon or hydrogen-argon mixture is introduced, the pressure is increased and the temperature is maintained to densify the composite material. After the heat maintenance is completed, the material is cooled with the furnace.

[0032] Surface processing: The surface reaction layer is removed by machining to produce composite shielding material splicing blocks.

[0033] In one specific embodiment, during hot pressing sintering, the pressure is increased to 30MPa~50MPa.

[0034] In one specific embodiment, during hot pressing sintering, the temperature is raised to 800℃~1000℃ and held for 60~120 minutes.

[0035] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0036] Currently, the operating temperature of lead-boron polyethylene shielding materials used in nuclear power plants and other nuclear facilities is generally no more than 120°C, and that of epoxy resin is no more than 160°C. However, the high-temperature resistant composite shielding material of this invention can withstand long-term operating temperatures exceeding 800°C, meeting the operating conditions of most reactors and expanding the application range of shielding materials. The shielding material has a high hydrogen content, exhibiting excellent combined neutron and gamma shielding performance. Its neutron and gamma shielding performance is comprehensively superior to that of existing lead-boron polyethylene, making it suitable for use on the inner side of nuclear reactor insulation layers. This significantly reduces the weight and volume of reactor shielding, thereby improving the flexibility of small reactors. Attached Figure Description

[0037] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0038] Figure 1 This is a SEM image of the high-temperature resistant composite shielding material prepared in Example 1 of the present invention; where 1 represents tungsten boride and 2 represents rare earth hydrides.

[0039] Figure 2 This is a SEM image of the high-temperature resistant composite shielding material prepared in Example 2 of the present invention;

[0040] Figure 3 This is a SEM image of the high-temperature resistant composite shielding material prepared in Example 3 of the present invention;

[0041] Figure 4 This is a SEM image of the high-temperature resistant composite shielding material prepared in Example 4 of the present invention;

[0042] Figure 5 This is a SEM image of the high-temperature resistant composite shielding material prepared in Example 5 of the present invention. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. The illustrative embodiments and descriptions of this invention are only used to explain this invention and are not intended to limit this invention.

[0044] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that these specific details are not necessary to practice the invention. In other embodiments, well-known materials or methods have not been specifically described in order to avoid obscuring the invention.

[0045] Throughout this specification, references to "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in connection with that embodiment or example is included in at least one embodiment of the invention. Therefore, the phrases "an embodiment," "an example," "an example," or "an example" appearing in various places throughout the specification do not necessarily refer to the same embodiment or example. Furthermore, specific features, structures, or characteristics can be combined in one or more embodiments or examples in any suitable combination and / or sub-combination. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described herein, as well as the features of those different embodiments or examples.

[0046] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for a specific parameter, it is understood that ranges of 60–110 and 80–120 are also expected. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0047] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0048] Example 1

[0049] This embodiment provides a method for preparing a high-temperature resistant composite shielding material based on metal hydrides. The material is prepared by hot pressing and sintering. The raw materials used are yttrium hydride and tungsten boride, with tungsten boride comprising 10% and the remainder being yttrium hydride. The density of the composite material is 4.6 g / cm³. 3 The specific steps are as follows:

[0050] S1. Preparation of rare earth hydride powder: Yttrium sponge is placed in a high-vacuum heating furnace and evacuated to 10°C. -4 Pa, heat to 700℃, hold for 30 minutes, and after the temperature inside the sintering furnace stabilizes, introduce high-purity hydrogen to make the furnace pressure slightly higher than 1 atmosphere, hold for 4 hours to allow the rare earth metal to fully permeate with hydrogen, and then cool down with the furnace after the holding period; then transfer the rare earth metal hydride to an atmosphere-protected glove box, crush it in the glove box, grind it into powder, and pass it through a 200-mesh sieve to obtain yttrium hydride powder.

[0051] S2. Mixing: Weigh 10g of tungsten boride and 90g of yttrium hydride powder prepared in step S1, put them into a mixer, fill the mixer with rubber balls, rotate at 30 rpm, and mix for 30 minutes.

[0052] S3. Pour the powder from step S2 into a graphite or silicon carbide mold and compact it.

[0053] S4. Place the mold containing the powder into a hot press furnace, fill it with high-purity argon gas, pressurize it to 30MPa, heat it to 1000℃, and hold it for 120 minutes to densify the composite material. After the holding period, cool it with the furnace.

[0054] S5. Surface processing: The surface reaction layer is removed by machining to produce composite shielding material splicing blocks.

[0055] like Figure 1 The image shown is an SEM image of the composite material splice block sample prepared in this embodiment. As can be seen from the image, tungsten boride is evenly distributed in the hydride and the material is dense.

[0056] Example 2

[0057] This embodiment provides a method for preparing a high-temperature resistant composite shielding material based on metal hydrides. Unlike Embodiment 1, this embodiment uses hot isostatic pressing (HIP) sintering. The raw materials used are yttrium hydride and tungsten boride, with tungsten boride comprising 70% and the remainder being yttrium hydride. The density of the composite material is 8.6 g / cm³. 3 The specific steps are as follows:

[0058] S1. Preparation of rare earth hydride powder: Yttrium sponge is placed in a high-vacuum heating furnace and evacuated to 10°C. -4 Pa, heat to 1000℃, hold for 30 minutes, and after the temperature inside the sintering furnace stabilizes, introduce high-purity hydrogen to make the gas pressure inside the furnace slightly higher than 1 atmosphere, hold for 4 hours to allow the rare earth metal to fully permeate with hydrogen, and then cool down with the furnace after the holding period; then transfer the rare earth metal hydride to an atmosphere-protected glove box, crush it in the glove box, grind it into powder, and pass it through a 200-mesh sieve to obtain yttrium hydride powder.

[0059] S2 Mixing: Weigh 70g of tungsten boride and 30g of yttrium hydride powder prepared in step S1, put them into a mixer, fill the mixer with rubber balls, rotate at 30 rpm, and mix for 30 minutes.

[0060] S3. Assembly: Place the mixed powder into a stainless steel sleeve, compact it with a hydraulic press to achieve a powder filling density of 55%, cover it with a cover plate with an exhaust pipe, and weld the cover plate to the sleeve.

[0061] S4. Exhausting and Vacuum Sealing: Connect the pre-welded casing to the vacuum exhaust station and evacuate to 10°C. -4 Pa, then heat the casing with heating equipment at a temperature of 500℃ for 5 hours until the vacuum reading is below 1 Pa. Immediately seal the exhaust pipe to maintain a high vacuum inside the casing.

[0062] S5. Hot isostatic pressing: The sizing and vacuum-sealed sizing is placed into a hot isostatic pressing furnace for hot isostatic pressing treatment at a pressure of 100 MPa, a temperature of 1000 degrees Celsius, and a holding time of 30 minutes. After the holding time is completed, the furnace is cooled down.

[0063] S6. Remove the sheath and surface finish: Remove the sheath by machining and treat the surface of the material to obtain a high-temperature resistant composite shielding material.

[0064] like Figure 2 The image shown is an SEM image of the composite material splice block sample prepared in this embodiment. It can be seen from the image that tungsten boride is evenly distributed in the hydride with a high volume fraction, and the material is dense.

[0065] Example 3

[0066] This embodiment provides a method for preparing a high-temperature resistant composite shielding material based on metal hydrides. Unlike Embodiment 1, this embodiment uses yttrium hydride and tungsten pentaboride as raw materials, with tungsten pentaboride comprising 20% ​​and the remainder being yttrium hydride. The density of the composite material is 4.5 g / cm³. 3 The specific steps are as follows:

[0067] S1. Preparation of rare earth hydride powder: Yttrium sponge is placed in a high-vacuum heating furnace and evacuated to 10°C. -4 Pa, heat to 900℃, hold for 30 minutes, and after the temperature inside the sintering furnace stabilizes, introduce high-purity hydrogen to make the furnace pressure slightly higher than 1 atmosphere, hold for 4 hours to allow the rare earth metal to fully infiltrate with hydrogen, and then cool down with the furnace after the holding period; then transfer the rare earth metal hydride to an atmosphere-protected glove box, crush it in the glove box, grind it into powder, and pass it through a 200-mesh sieve to obtain yttrium hydride powder.

[0068] S2. Mixing: Weigh 20g of tungsten pentaboride and 80g of yttrium hydride powder prepared in step S1, put them into a mixer, fill the mixer with rubber balls, rotate at 30 rpm, and mix for 30 minutes.

[0069] S3. Pour the powder from step S2 into a graphite or silicon carbide mold and compact it.

[0070] S4. Place the mold containing the powder into a hot press furnace, fill it with high-purity argon gas, pressurize it to 30MPa, heat it to 1000℃, and hold it for 120 minutes to densify the composite material. After the holding period, cool it with the furnace.

[0071] S5. Surface processing: The surface reaction layer is removed by machining to produce composite shielding material splicing blocks.

[0072] like Figure 3 The image shown is an SEM image of the composite material splice block sample prepared in this embodiment. It can be seen from the image that the material is relatively dense.

[0073] Example 4

[0074] This embodiment provides a method for preparing a high-temperature resistant composite shielding material based on metal hydrides. Unlike Embodiment 1, this embodiment uses cerium hydride and tungsten boride as raw materials, with tungsten boride comprising 10% and the remainder being cerium hydride. The density of the composite material is 5.7 g / cm³. 3 The specific steps are as follows:

[0075] S1. Preparation of rare earth hydride powder: Place sponge cerium into a high vacuum heating furnace and evacuate to 100°C. -4Pa, heat to 900℃, hold for 30 minutes, and after the temperature inside the sintering furnace stabilizes, introduce high-purity hydrogen to make the furnace pressure slightly higher than 1 atmosphere, hold for 4 hours to allow the rare earth metal to fully infiltrate with hydrogen, and then cool down with the furnace after the holding period; then transfer the rare earth metal hydride to an atmosphere-protected glove box, crush it, grind it into powder, and pass it through a 200-mesh sieve to obtain cerium hydride powder.

[0076] S2. Mixing: Weigh 10g of tungsten boride and 90g of cerium hydride powder prepared in step S1, put them into a mixer, fill the mixer with rubber balls, rotate at 30 rpm, and mix for 30 minutes.

[0077] S3. Pour the powder from step S2 into a graphite or silicon carbide mold and compact it.

[0078] S4. Place the mold containing the powder into a hot press furnace, fill it with high-purity argon gas, pressurize it to 30MPa, raise the temperature to 800℃, and hold it for 120 minutes to densify the composite material. After the holding period, cool it with the furnace.

[0079] S5. Surface processing: The surface reaction layer is removed by machining to produce composite shielding material splicing blocks. The cerium hydride material is protected by an atmosphere throughout the processing.

[0080] like Figure 4 The image shown is an SEM image of the composite material splice block sample prepared in this embodiment. It can be seen from the image that the material is relatively dense and has no obvious pores.

[0081] Example 5

[0082] This embodiment provides a method for preparing a high-temperature resistant composite shielding material based on metal hydrides. The material is prepared by hot pressing and sintering. The raw materials used are yttrium hydride and tungsten boride. Unlike Example 1, the tungsten boride content in this embodiment is 1%, with the balance being yttrium hydride. The density of the composite material is 4.4 g / cm³. 3 The specific steps are as follows:

[0083] S1. Preparation of rare earth hydride powder: Yttrium sponge is placed in a high-vacuum heating furnace and evacuated to 10°C. -4 Pa, heat to 900℃, hold for 30 minutes, and after the temperature inside the sintering furnace stabilizes, introduce high-purity hydrogen to make the furnace pressure slightly higher than 1 atmosphere, hold for 4 hours to allow the rare earth metal to fully infiltrate with hydrogen, and then cool down with the furnace after the holding period; then transfer the rare earth metal hydride to an atmosphere-protected glove box, crush it in the glove box, grind it into powder, and pass it through a 200-mesh sieve to obtain yttrium hydride powder.

[0084] S2. Mixing: Weigh 1g of tungsten boride and 99g of yttrium hydride powder prepared in step S1, put them into a mixer, fill the mixer with rubber balls, rotate at 30 rpm, and mix for 30 minutes.

[0085] S3. Pour the powder from step S2 into a graphite or silicon carbide mold and compact it.

[0086] S4. Place the mold containing the powder into a hot press furnace, fill it with high-purity argon gas, pressurize it to 30MPa, heat it to 900℃, and hold it for 120 minutes to densify the composite material. After the holding period, cool it with the furnace.

[0087] S5. Surface processing: The surface reaction layer is removed by machining to produce composite shielding material splicing blocks.

[0088] like Figure 5 The image shown is an SEM image of the composite material splice block sample prepared in this embodiment. It can be seen from the image that the material is relatively dense and has no obvious pores.

[0089] Comparative Example 1

[0090] This embodiment provides a method for preparing a composite shielding material based on metal hydrides. The material is prepared by hot pressing and sintering. The raw materials used are yttrium hydride and tungsten boride. Unlike Example 1, the tungsten boride content in this comparative example is 0.5%, with the balance being yttrium hydride. The density of the composite material is 4.3 g / cm³. 3 The specific steps are as follows:

[0091] S1. Preparation of rare earth hydride powder: Yttrium sponge is placed in a high-vacuum heating furnace and evacuated to 10°C. -4 Pa, heat to 700℃, hold for 30 minutes, and after the temperature inside the sintering furnace stabilizes, introduce high-purity hydrogen to make the furnace pressure slightly higher than 1 atmosphere, hold for 4 hours to allow the rare earth metal to fully permeate with hydrogen, and then cool down with the furnace after the holding period; then transfer the rare earth metal hydride to an atmosphere-protected glove box, crush it in the glove box, grind it into powder, and pass it through a 200-mesh sieve to obtain yttrium hydride powder.

[0092] S2. Mixing: Weigh 0.5g of tungsten boride and 99.5g of yttrium hydride powder prepared in step S1, put them into a mixer, fill the mixer with rubber balls, rotate at 30 rpm, and mix for 30 minutes.

[0093] S3. Pour the powder from step S2 into a graphite or silicon carbide mold and compact it.

[0094] S4. Place the mold containing the powder into a hot press furnace, fill it with high-purity argon gas, pressurize it to 30MPa, heat it to 1000℃, and hold it for 120 minutes to densify the composite material. After the holding period, cool it with the furnace.

[0095] S5. Surface processing: The surface reaction layer is removed by machining to produce composite shielding material splicing blocks.

[0096] Comparative Example 2

[0097] This embodiment provides a method for preparing a composite shielding material based on metal hydrides. The material is prepared by hot pressing and sintering, using yttrium hydride and tungsten boride as raw materials. Unlike Example 1, the tungsten boride content in this comparative example is 75%, with the balance being yttrium hydride. The density of the composite material is 7.6 g / cm³. 3 The material is difficult to sinter into a dense state. The specific steps are as follows:

[0098] S1. Preparation of rare earth hydride powder: Yttrium sponge is placed in a high-vacuum heating furnace and evacuated to 10°C. -4 Pa, heat to 700℃, hold for 30 minutes, and after the temperature inside the sintering furnace stabilizes, introduce high-purity hydrogen to make the furnace pressure slightly higher than 1 atmosphere, hold for 4 hours to allow the rare earth metal to fully permeate with hydrogen, and then cool down with the furnace after the holding period; then transfer the rare earth metal hydride to an atmosphere-protected glove box, crush it in the glove box, grind it into powder, and pass it through a 200-mesh sieve to obtain yttrium hydride powder.

[0099] S2. Mixing: Weigh 75g of tungsten boride and 25g of yttrium hydride powder prepared in step S1, put them into a mixer, fill the mixer with rubber balls, rotate at 30 rpm, and mix for 30 minutes.

[0100] S3. Pour the powder from step S2 into a graphite or silicon carbide mold and compact it.

[0101] S4. Place the mold containing the powder into the hot press furnace, fill it with high-purity argon gas, pressurize it to 30MPa, heat it to 1000℃, hold it at that temperature for 120 minutes, and then cool it with the furnace after the holding time is over.

[0102] S5. Surface processing: The surface reaction layer is removed by machining to produce composite shielding material splicing blocks.

[0103] The shielding efficiency of the shielding materials prepared by the methods of Examples 1-5 and Comparative Examples 1-2 was tested, and boron carbide ceramics and lead-boron polyethylene were set as comparisons. The test results are shown in Table 1.

[0104] Table 1

[0105] Example 1 4.6 1000℃ 21.6% 76.3% Example 2 8.6 1000℃ 37.2% 75.2% Example 3 4.5 1000℃ 21.4% 75.9% Example 4 5.7 900℃ 26.1% 74.5% Example 5 4.3 1000℃ 20.2% 75.9% Comparative Example 1 4.3 1000℃ 20.1% 74.1% Comparative Example 2 4.2 1000℃ 20% 71.6% boron carbide ceramics 2.5 800℃ 12.5% 64.1% Lead-boron polyethylene 3.4 120℃ 18.2% 73.5%

[0106] According to the above test results, the gamma shielding performance and fast neutron shielding performance of the shielding material prepared by the method of the present invention are better than those of Comparative Example 1 and Comparative Example 2, and also better than boron carbide ceramic and lead boron polyethylene. The material prepared by Comparative Example 2 has low density.

[0107] Finally, it should be noted that the specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention. It is obvious to those skilled in the art that this application is not limited to the details of the above exemplary embodiments, and that the present application can be implemented in other specific forms without departing from the spirit or basic characteristics of the present application. Therefore, the embodiments should be considered exemplary and non-limiting in all respects. The scope of this application is defined by the appended claims rather than the foregoing description, and therefore all changes falling within the meaning and scope of the equivalents of the claims are intended to be included within this application.

Claims

1. A high-temperature resistant composite shielding material based on metal hydrides, characterized in that, The high-temperature resistant composite shielding material is composed of rare earth metal hydrides and tungsten boride; the mass percentage of the tungsten boride is 1% to 70%, and the mass percentage of the rare earth hydrides is 30% to 99%.

2. The high-temperature resistant composite shielding material based on metal hydride according to claim 1, characterized in that, The rare earth metal hydrides include any one or a mixture of two of the following components: yttrium hydride, gadolinium hydride, cerium hydride, and lanthanum hydride.

3. The high-temperature resistant composite shielding material based on metal hydride according to claim 1, characterized in that, The tungsten boride material includes any one or a mixture of two of the following components: tungsten monoboride, tungsten diboride, tungsten pentaboride, and tungsten diboride.

4. A method for preparing a high-temperature resistant composite shielding material based on metal hydrides, characterized in that, The method includes preparation by hot isostatic pressing (HIP) or hot pressing sintering; the HIP method is used for the preparation of large-size high-temperature resistant composite shielding materials, and the hot pressing sintering method is used for the preparation of small-size spliced ​​shielding plates.

5. The method for preparing a high-temperature resistant composite shielding material based on metal hydrides according to claim 4, characterized in that, The preparation of large-size high-temperature resistant composite shielding materials using the hot isostatic pressing sintering method includes the following steps: Preparation of rare earth hydride powder: Rare earth metal is placed in a high vacuum heating furnace, vacuumed and heated. After the temperature in the heating furnace stabilizes, hydrogen is introduced to allow the rare earth metal to fully permeate with hydrogen. After holding at the temperature, it is cooled down with the furnace and then crushed to obtain rare earth metal hydride powder. Mixing: Place rare earth hydride powder and tungsten boride powder into a mixer and mix evenly according to the proportion; Assembly: Place the mixed powder into a stainless steel sleeve and compact it, cover it with a cover plate with an exhaust pipe, and weld the cover plate to the sleeve; Exhaust and vacuum sealing: Connect the pre-welded casing to the vacuum exhaust station, heat the casing after evacuation, and then seal the exhaust pipe to maintain a high vacuum inside the casing. Hot isostatic pressing (HIP): The sizing and vacuum-sealed sizing jacket is placed into a hot isostatic pressing furnace for hot isostatic pressing. Remove the sheath and surface finish: After removing the sheath by machining, a high-temperature resistant composite shielding material is obtained.

6. The method for preparing a high-temperature resistant composite shielding material based on metal hydrides according to claim 5, characterized in that, Vacuum up to 10 -4 Pa~10 -2 Pa.

7. The method for preparing a high-temperature resistant composite shielding material based on metal hydrides according to claim 5, characterized in that, After vacuuming, the temperature is raised to 700℃~900℃.

8. The method for preparing a high-temperature resistant composite shielding material based on metal hydrides according to claim 5, characterized in that, When mixing materials, put rubber balls into the mixer and control the rotation speed at 30~90 rpm.

9. The method for preparing a high-temperature resistant composite shielding material based on metal hydrides according to claim 5, characterized in that, During assembly, the powder filling density is made to reach 55%~65%.

10. The method for preparing a high-temperature resistant composite shielding material based on metal hydrides according to claim 5, characterized in that, During hot isostatic pressing, the pressure is controlled at 100MPa~200MPa.

11. The method for preparing a high-temperature resistant composite shielding material based on metal hydrides according to claim 5, characterized in that, The temperature during hot isostatic pressing is controlled at 800℃~1000℃. After heat preservation and pressure holding are completed, the temperature is cooled to below 700℃ before depressurization.

12. The method for preparing a high-temperature resistant composite shielding material based on metal hydrides according to claim 5, characterized in that, The hot-pressing sintering method used for small-sized spliced ​​shielding panels includes the following steps: Preparation of rare earth hydride powder: Rare earth metal is placed in a high vacuum heating furnace, vacuumed and heated. After the temperature in the heating furnace stabilizes, hydrogen is introduced to allow the rare earth metal to fully permeate with hydrogen. After holding at the temperature, it is cooled down with the furnace and then crushed to obtain rare earth metal hydride powder. Mixing: Place rare earth hydride powder and tungsten boride powder into a mixer and mix evenly according to the proportion; pour the mixed powder into a graphite or silicon carbide mold and compact it; Hot pressing sintering: The mold containing powder is placed into a hot press furnace, high-purity argon or hydrogen-argon mixture is introduced, the pressure is increased and the temperature is maintained to densify the composite material. After the heat maintenance is completed, the material is cooled with the furnace. Surface processing: The surface reaction layer is removed by machining to produce composite shielding material splicing blocks.

13. The method for preparing a high-temperature resistant composite shielding material based on metal hydrides according to claim 12, characterized in that, During hot pressing and sintering, the pressure is increased to 30MPa~50MPa.

14. The method for preparing a high-temperature resistant composite shielding material based on metal hydrides according to claim 12, characterized in that, During hot pressing and sintering, the temperature is raised to 800℃~1000℃ and held for 60~120 minutes.

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