High temperature resistant yttrium-gadolinium hydride neutron moderator absorber and method of manufacture
The yttrium-gadolinium hydride neutron moderator absorber was manufactured by a pre-hydrogenation-cold pressing-sintering process, which solved the problems of uneven material mixing and cracking at high temperatures, and achieved the preparation of a highly efficient neutron shielding material with good fast neutron moderation and thermal neutron absorption performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANGHAI NUCLEAR ENGINEERING RESEARCH & DESIGN INSTITUTE CO LTD
- Filing Date
- 2025-11-13
- Publication Date
- 2026-07-31
AI Technical Summary
Existing technologies struggle to stably use yttrium-gadolinium hydride composites as neutron shielding materials at high temperatures, exhibiting issues such as uneven mixing and cracking, and lacking effective manufacturing processes.
The process of pre-hydrogenation-cold pressing-sintering is adopted. First, yttrium powder and gadolinium powder are pre-hydrogenated, then mixed and cold-pressed, and finally hydrogenated and sintered under high temperature and high pressure to form a uniform yttrium-gadolinium hydride neutron moderator absorber.
Neutron shielding materials with good fast neutron moderation and thermal neutron absorption properties were manufactured. The finished products are not prone to cracking, have a high yield, and exhibit good high-temperature stability.
Smart Images
Figure CN121426564B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of nuclear power, specifically relating to a high-temperature resistant yttrium-gadolinium hydride neutron moderator and its manufacturing method. Background Technology
[0002] With the development of nuclear power technology, the operating temperature of new reactors is further increasing. Some technical solutions require reactor neutron shielding materials to operate stably for extended periods at temperatures of 600℃-1000℃, exceeding the upper temperature limits of traditional neutron shielding materials such as lithium hydride and zirconium hydride. Among new neutron shielding materials, yttrium hydride possesses a high decomposition temperature and excellent fast neutron moderation capability, thus it is considered to have promising application prospects. However, the application range of yttrium hydride is limited by its insufficient thermal neutron absorption capacity. Gadolinium atoms have a very high thermal neutron absorption cross section, and the combination of yttrium and gadolinium shows good application prospects. However, currently, there is a lack of effective manufacturing processes for yttrium-gadolinium composite materials. Therefore, providing a manufacturing method for a yttrium-gadolinium hydride neutron moderator absorber has high practical value. Summary of the Invention
[0003] The purpose of this invention is to provide a method for manufacturing a high-temperature resistant yttrium-gadolinium hydride neutron moderator absorber, thereby producing a shielding material with good fast neutron moderation and thermal neutron absorption properties. This invention also provides a high-temperature resistant yttrium-gadolinium hydride neutron moderator absorber.
[0004] According to one aspect of the present invention, a method for manufacturing a high-temperature resistant yttrium-gadolinium hydride neutron moderator absorber is provided, the method comprising the following steps:
[0005] Step a): Yttrium powder and gadolinium powder are provided and pre-hydrogenated respectively. The temperature of the pre-hydrogenation treatment is 200℃-900℃ and the hydrogen pressure is 0.01MPa-0.5MPa, to obtain yttrium hydride raw material powder and gadolinium hydride raw material powder.
[0006] Step b): Mix the yttrium hydride raw material powder and the gadolinium hydride raw material powder evenly, so that Gd accounts for 1%-30% by weight, to obtain a mixed powder;
[0007] Step c): The mixed powder is cold-pressed to obtain a cold-pressed blank;
[0008] Step d): The cold-pressed blank is subjected to hydrogenation sintering at a heating temperature of 900℃-1400℃ and a hydrogen pressure of 0.05MPa-1MPa to obtain a high-temperature resistant yttrium-gadolinium hydride neutron moderator absorber.
[0009] This method can effectively manufacture neutron shielding materials with good fast neutron moderation and thermal neutron absorption properties. The finished products are not prone to cracking and have a high yield.
[0010] Furthermore, in some embodiments, the average particle size of the yttrium powder and the gadolinium powder is 100-400 mesh. Controlling the particle size of the powder raw materials helps to improve the uniformity of the finished product, increase reaction efficiency, and prevent uneven hydrogenation.
[0011] Furthermore, in some embodiments, the pre-hydrogenation time in step a) is 1h-24h.
[0012] Furthermore, in some embodiments, in step b), a mixer is used to mix the yttrium hydride raw material powder and the gadolinium hydride raw material powder.
[0013] Furthermore, in some embodiments, in step b), the mixing speed is 10 r / min-100 r / min, and the mixing time is 0.5 h-24 h.
[0014] Furthermore, in some embodiments, in step c), the cold pressing pressure is 50MPa-300MPa, and the holding time is 1min-30min.
[0015] Furthermore, in some embodiments, the sintering time in step d) is 1h-24h.
[0016] According to another embodiment of the present invention, a high-temperature resistant yttrium-gadolinium hydride neutron moderator is provided, manufactured using the manufacturing method of the high-temperature resistant yttrium-gadolinium hydride neutron moderator provided in any of the foregoing embodiments. This neutron moderator, as a neutron shielding material, exhibits excellent fast neutron moderation and thermal neutron absorption performance, and demonstrates good stability under high-temperature conditions. Attached Figure Description
[0017] Figure 1 A photograph of the finished product of the high-temperature resistant yttrium-gadolinium hydride neutron moderator absorber in one embodiment;
[0018] Figure 2 An X-ray photograph of a high-temperature resistant yttrium-gadolinium hydride neutron moderator absorber in one embodiment;
[0019] Figure 3 This is an X-ray diffraction pattern of a high-temperature resistant yttrium-gadolinium hydride neutron moderator absorber in one embodiment;
[0020] Figure 4 This is a high-temperature dehydrogenation curve of a high-temperature resistant yttrium-gadolinium hydride neutron moderator absorber in one embodiment.
[0021] The purpose of the above figures is to provide a detailed description of the invention so that those skilled in the art can understand the technical concept of the invention, and not to limit the invention. Detailed Implementation
[0022] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings.
[0023] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment herein. The phrase appearing in various places in the specification does not necessarily refer to the same embodiment, nor is it limited to mutually exclusive, independent, or alternative embodiments. Those skilled in the art will understand that the embodiments herein can be combined with other embodiments without causing structural conflicts.
[0024] In this article, "multiple" means at least two.
[0025] With the rapid development of civilian nuclear power technology, the operating temperature of new reactor cores is constantly increasing to further improve reactor economics. In some advanced reactor designs, the operating temperature of neutron shielding materials has reached 600℃-1000℃, which is comparable to the decomposition temperature of conventional metal hydride shielding materials such as lithium hydride and zirconium hydride. Yttrium hydride has an even higher decomposition temperature and better stability at high temperatures, while also exhibiting good moderation performance for fast neutrons. Therefore, it has promising applications as a neutron shielding material in new reactors. However, yttrium hydride itself has insufficient thermal neutron absorption capacity, making it difficult to use directly as a neutron shielding material alone. Gadolinium has a thermal neutron absorption cross-section of 46,000 barn, making it a good thermal neutron absorber. However, mixing yttrium hydride with gadolinium can easily lead to problems such as uneven mixing or cracking under long-term service conditions. Currently, there is a lack of effective technical solutions to prepare yttrium-gadolinium composite neutron moderators and absorbers with a certain volume.
[0026] To overcome the aforementioned shortcomings of the prior art, one embodiment of the present invention provides a method for manufacturing a high-temperature resistant yttrium-gadolinium hydride neutron moderator absorber. The method specifically includes the following steps:
[0027] Step a): Yttrium powder and gadolinium powder are provided as raw materials and subjected to pre-hydrogenation treatment respectively. Specifically, in a preferred embodiment, the average particle size of yttrium powder and gadolinium powder is 100-400 mesh. The pre-hydrogenation treatment is carried out in a hydrogenation furnace at a heating temperature of 200℃-900℃ and a hydrogen pressure of 0.01MPa-0.5MPa. Depending on the particle size and total amount of metal powder, the pre-hydrogenation treatment time is 1h-24h. After the pre-hydrogenation treatment, yttrium hydride raw material powder and gadolinium hydride raw material powder are obtained. Random sampling and detection of the absence of unhydrogenated pure metal particles is considered as the completion of the pre-hydrogenation treatment. By controlling the pre-hydrogenation parameters, insufficient hydrogenation of yttrium powder and gadolinium powder can be avoided when the temperature is too low, while excessively high temperatures can prevent hydrogen desorption and powder sintering, ensuring the formability of the subsequent materials. The hydrogen pressure can provide sufficient reaction driving force for the hydrogenation reaction, improving the uniformity and consistency of the powder composition after pre-hydrogenation.
[0028] Step b): Mix the yttrium hydride raw material powder and gadolinium hydride raw material powder evenly to obtain a mixed powder. After mixing, the weight ratio of Gd is 1%-30%. Specifically, the mixing process is carried out by mechanical stirring using a mixer. The mixer speed is 10r / min-100r / min, and the mixing time is 0.5h-24h. By controlling the mixing parameters, the uniformity and consistency of the mixed powder can be improved, preventing uneven mixing and component segregation caused by excessively low speed and short mixing time, and avoiding the risk of dehydrogenation due to excessively high internal energy of hydrides caused by excessively high speed and long mixing time.
[0029] Step c): The mixed powder is cold-pressed to obtain a cold-pressed preform. Specifically, the cold-pressing pressure is 50MPa-300MPa, and the holding time is 1min-30min. Cold pressing can effectively improve the uniformity of the material, reduce anisotropy and internal stress, and improve the yield in the subsequent hydrogenation sintering process. Too low a pressure can easily lead to insufficient density and molding failure, while too high a pressure can easily lead to excessive internal stress, increasing the risk of cracking or delamination in the subsequent hydrogenation sintering process.
[0030] Step d): The cold-pressed billet is hydrogenated and sintered in a high-temperature and high-pressure hydrogenation furnace to obtain a high-temperature resistant yttrium-gadolinium hydride neutron moderator absorber. The heating temperature for hydrogenation and sintering is 900℃-1400℃, the hydrogen pressure is 0.05MPa-1MPa, and the sintering time is set to 1h-24h depending on the size of the cold-pressed billet.
[0031] In the conventional hydrogenation process of dense bulk metal materials, hydrogen atoms first react with the material surface to form metal hydrides. Hydrogen atoms gradually diffuse into the interior of the material, but diffusion within the dense bulk is relatively slow, easily leading to a significant hydrogen concentration gradient during hydrogenation. The surface reacts fully with hydrogen atoms, while the interior has a lower hydrogen concentration, making it easier for different phases to form. Due to differences in lattice distortion and volume expansion, excessive internal stress occurs, causing crack formation. This invention employs a pre-hydrogenation-cold pressing-sintering process. First, yttrium powder and gadolinium powder are pre-hydrogenated to generate high-hydrogen-content yttrium hydride and gadolinium hydride powders. Then, the yttrium hydride and gadolinium hydride powders are mixed in a specific ratio to form a uniformly distributed mixture. This mixture is then cold-pressed into a bulk blank of the designed shape, and finally, the blank is sintered with hydrogen. The above embodiments utilize a metal powder pre-hydrogenation process to increase the hydrogen content of the material, weaken the dehydrogenation effect caused by high temperature, and increase the hydrogen atom density of the final yttrium-gadolinium hydride material. A low-density billet is prepared by a cold pressing process. The densification shrinkage of the low-density billet during high-temperature hydrogenation sintering effectively offsets the volume expansion effect during hydrogenation, avoiding cracks caused by excessive internal stress in the material.
[0032] In a first preferred embodiment, the method for manufacturing the yttrium-gadolinium hydride neutron moderator absorber is as follows:
[0033] First, yttrium powder and gadolinium powder with a particle size of 200 mesh are used as raw materials and loaded into a hydrogenation furnace. After evacuation, hydrogen is introduced to atmospheric pressure, followed by evacuation again, and hydrogen is used to wash away impurities in the furnace. Next, hydrogen gas at a pressure of 0.05 MPa is introduced into the hydrogenation furnace, and the furnace is heated to 600°C and held for 3 hours to complete the pre-hydrogenation treatment, obtaining yttrium hydride raw material powder and gadolinium hydride raw material powder.
[0034] Next, yttrium hydride raw material powder and gadolinium hydride raw material powder are mixed to achieve a Gd mass percentage of 7%, and then loaded into a mixer. The mixture is stirred at a speed of 50 r / min for 5 hours under an argon atmosphere to obtain a uniform mixed powder.
[0035] Next, the mixed powder is loaded into a cold press mold, and the entire cold press mold is loaded into a cold press machine. The press is held at 200MPa for 5 minutes to form a cold press blank.
[0036] Finally, the cold-pressed billet is placed into a high-temperature, high-pressure hydrogenation furnace. Impurities are removed by two gas washing operations using hydrogen gas. Then, hydrogen gas at 0.1 MPa is introduced, and the furnace is heated to 1300°C and held for 4 hours to complete the hydrogenation sintering. The hydrogen atmosphere is maintained until the furnace cools to room temperature, yielding the desired product. Figure 1 The high-temperature resistant yttrium-gadolinium hydride neutron moderator is shown. X-ray analysis of this neutron moderator yielded the following results: Figure 2 As shown, the material block is uniformly dense internally, without cracks, pores, or other defects. The X-ray diffraction results are as follows: Figure 3 As shown, hydrogenation is complete, with virtually no unhydrogenated pure metal components remaining. High-temperature decomposition tests were conducted on this neutron moderator absorber, and the results are as follows... Figure 4 As shown, dehydrogenation basically does not occur at 800℃, and the weight loss due to dehydrogenation does not exceed 0.1% at temperatures not exceeding 1000℃, indicating good high-temperature stability.
[0037] In a second preferred embodiment, the method for manufacturing the yttrium-gadolinium hydride neutron moderator absorber is as follows:
[0038] First, yttrium powder and gadolinium powder with a particle size of 100 mesh are used as raw materials and loaded into a hydrogenation furnace. After evacuation, hydrogen is introduced to atmospheric pressure, followed by evacuation again. Impurities in the furnace are removed by hydrogen scrubbing. Next, hydrogen gas at a pressure of 0.5 MPa is introduced into the hydrogenation furnace, and the furnace is heated to 900°C and held for 24 hours to complete the pre-hydrogenation treatment, obtaining yttrium hydride raw material powder and gadolinium hydride raw material powder.
[0039] Next, the yttrium hydride raw material powder and gadolinium hydride raw material powder are mixed to achieve a Gd mass percentage of 1%, and then loaded into a mixer. Under the protection of argon atmosphere, the mixture is mixed at a speed of 10 r / min for 24 h to obtain a uniform mixed powder.
[0040] Next, the mixed powder is loaded into a cold press mold, and the entire cold press mold is loaded into a cold press machine. The press is held at 250 MPa for 1 minute to form a cold press blank.
[0041] Finally, the cold-pressed blank is placed into a high-temperature and high-pressure hydrogenation furnace, and impurity gases are removed by two gas washing operations using hydrogen. Then, 1 MPa of hydrogen is introduced, and the hydrogenation furnace is heated to 1400℃ and held for 1 hour to complete the hydrogenation sintering, thus obtaining a high-temperature resistant yttrium-gadolinium hydride neutron moderator absorber.
[0042] In the third preferred embodiment, the method for manufacturing the yttrium-gadolinium hydride neutron moderator absorber is as follows:
[0043] First, yttrium powder and gadolinium powder with a particle size of 400 mesh were used as raw materials and loaded into a hydrogenation furnace. After evacuation, hydrogen was introduced to atmospheric pressure, followed by evacuation again. Impurities in the furnace were removed by hydrogen scrubbing. Next, hydrogen gas at a pressure of 0.01 MPa was introduced into the hydrogenation furnace, and the furnace was heated to 200°C and held for 1 hour to complete the pre-hydrogenation treatment, obtaining yttrium hydride raw material powder and gadolinium hydride raw material powder.
[0044] Next, the yttrium hydride raw material powder and the gadolinium hydride raw material powder are mixed to achieve a Gd mass percentage of 30%. The mixture is then placed in a mixer and mixed at a speed of 100 r / min for 1 hour under an argon atmosphere to obtain a uniform mixed powder.
[0045] Next, the mixed powder is loaded into a cold press mold, and the entire cold press mold is loaded into a cold press machine. The press is held at 50 MPa for 30 minutes to form a cold press blank.
[0046] Finally, the cold-pressed blank is placed into a high-temperature and high-pressure hydrogenation furnace, and impurity gases are removed by two gas washing operations using hydrogen. Then, 0.05 MPa of hydrogen is introduced, and the hydrogenation furnace is heated to 900°C and held for 24 hours to complete the hydrogenation sintering, thus obtaining a high-temperature resistant yttrium-gadolinium hydride neutron moderator absorber.
[0047] In the fourth preferred embodiment, the method for manufacturing the yttrium-gadolinium hydride neutron moderator absorber is as follows:
[0048] First, yttrium powder and gadolinium powder with a particle size of 300 mesh were used as raw materials and loaded into a hydrogenation furnace. After evacuation, hydrogen was introduced to atmospheric pressure, followed by evacuation again, and hydrogen was used to wash away impurities in the furnace. Next, hydrogen gas at a pressure of 0.3 MPa was introduced into the hydrogenation furnace, and the furnace was heated to 400°C and held for 12 hours to complete the pre-hydrogenation treatment, obtaining yttrium hydride raw material powder and gadolinium hydride raw material powder.
[0049] Next, yttrium hydride raw material powder and gadolinium hydride raw material powder are mixed to achieve a Gd mass percentage of 15%, and then loaded into a mixer. The mixture is stirred at a speed of 70 r / min for 10 h under an argon atmosphere to obtain a uniform mixed powder.
[0050] Next, the mixed powder is loaded into a cold press mold, and the entire cold press mold is loaded into a cold press machine. The press is held at 150MPa for 20 minutes to form a cold press blank.
[0051] Finally, the cold-pressed blank is placed into a high-temperature and high-pressure hydrogenation furnace, and impurity gases are removed by two gas washing operations using hydrogen. Then, 0.3 MPa of hydrogen is introduced, and the hydrogenation furnace is heated to 1100℃ and held for 12 hours to complete the hydrogenation sintering, thus obtaining a high-temperature resistant yttrium-gadolinium hydride neutron moderator absorber.
[0052] In the fifth preferred embodiment, the method for manufacturing the yttrium-gadolinium hydride neutron moderator absorber is as follows:
[0053] First, yttrium powder and gadolinium powder with a particle size of 200 mesh were used as raw materials and loaded into a hydrogenation furnace. After evacuation, hydrogen was introduced to atmospheric pressure, followed by evacuation again. Impurities in the furnace were removed by hydrogen scrubbing. Next, hydrogen gas at a pressure of 0.1 MPa was introduced into the hydrogenation furnace, and the furnace was heated to 300°C and held for 20 hours to complete the pre-hydrogenation treatment, yielding yttrium hydride raw material powder and gadolinium hydride raw material powder.
[0054] Next, the yttrium hydride raw material powder and gadolinium hydride raw material powder are mixed to achieve a Gd mass percentage of 20%, and then loaded into a mixer. Under the protection of argon atmosphere, the mixture is mixed at a speed of 30 r / min for 16 h to obtain a uniform mixed powder.
[0055] Next, the mixed powder is loaded into a cold press mold, and the entire cold press mold is loaded into a cold press machine. The press is held at 200MPa for 10 minutes to form a cold press blank.
[0056] Finally, the cold-pressed blank is placed into a high-temperature and high-pressure hydrogenation furnace, and impurity gases are removed by two gas washing operations using hydrogen. Then, 0.8 MPa of hydrogen is introduced, and the hydrogenation furnace is heated to 1200℃ and held for 8 hours to complete the hydrogenation sintering, thus obtaining a high-temperature resistant yttrium-gadolinium hydride neutron moderator absorber.
[0057] The purpose of the above embodiments is to provide a further detailed description of the present invention in conjunction with the accompanying drawings, so that those skilled in the art can understand the technical concept of the present invention. Within the scope of the present invention, any optimization or equivalent substitution of the technical features involved, or any combination of implementation methods in different embodiments without causing a conflict of principles, shall fall within the protection scope of the present invention.
Claims
1. A method of manufacturing a high temperature resistant yttrium-gadolinium hydride neutron moderator absorber, characterized by, Includes the following steps: Step a): Yttrium powder and gadolinium powder are provided and pre-hydrogenated respectively. The temperature of the pre-hydrogenation treatment is 200℃-900℃ and the hydrogen pressure is 0.01MPa-0.5MPa, to obtain yttrium hydride raw material powder and gadolinium hydride raw material powder. Step b): Mix the yttrium hydride raw material powder and the gadolinium hydride raw material powder evenly, so that Gd accounts for 1%-30% by weight, to obtain a mixed powder; Step c): The mixed powder is cold-pressed to obtain a cold-pressed blank; Step d): The cold-pressed blank is subjected to hydrogenation sintering at a heating temperature of 900℃-1400℃ and a hydrogen pressure of 0.05MPa-1MPa to obtain a high-temperature resistant yttrium-gadolinium hydride neutron moderator absorber.
2. The method of producing a high-temperature-resistant yttrium-gadolinium hydride neutron moderator absorber according to claim 1, characterized by, The average particle size of the yttrium powder and the gadolinium powder is 100-400 mesh.
3. The method for manufacturing the high-temperature resistant yttrium-gadolinium hydride neutron moderator absorber according to claim 1, characterized in that, The pre-hydrogenation time in step a) is 1h-24h.
4. The method for manufacturing the high-temperature resistant yttrium-gadolinium hydride neutron moderator absorber according to claim 1, characterized in that, In step b), a mixer is used to mix the yttrium hydride raw material powder and the gadolinium hydride raw material powder.
5. The method for manufacturing the high-temperature resistant yttrium-gadolinium hydride neutron moderator absorber according to claim 4, characterized in that, In step b), the mixing speed is 10 r / min-100 r / min, and the mixing time is 0.5 h-24 h.
6. The method for manufacturing the high-temperature resistant yttrium-gadolinium hydride neutron moderator absorber according to claim 1, characterized in that, In step c), the pressure for cold pressing is 50MPa-300MPa, and the holding time is 1min-30min.
7. The method for manufacturing the high-temperature resistant yttrium-gadolinium hydride neutron moderator absorber according to claim 1, characterized in that, In step d), the sintering time is 1h-24h.
8. A high-temperature resistant yttrium-gadolinium hydride neutron moderator absorber, characterized in that, It is manufactured using the manufacturing method of the high-temperature resistant yttrium-gadolinium hydride neutron moderator absorber as described in any one of claims 1 to 7.