High-temperature-resistant yttrium-gadolinium hydride neutron moderation absorber and manufacturing method thereof

Abstract

The invention discloses a high-temperature-resistant yttrium-gadolinium hydride neutron moderation absorber and a manufacturing method thereof, and belongs to the field of nuclear power. The manufacturing method of the high-temperature-resistant yttrium-gadolinium hydride neutron moderation absorber comprises the following steps: performing pre-hydrogenation treatment on yttrium powder and gadolinium powder, uniformly mixing the yttrium powder and the gadolinium powder to obtain mixed powder, performing cold press molding on the mixed powder, and then performing hydrogenation sintering to obtain the high-temperature-resistant yttrium-gadolinium hydride neutron moderation absorber. According to the method, the cracking risk of the neutron moderation absorber in the sintering process can be effectively reduced, and the neutron moderation absorber with good fast neutron moderation performance and thermal neutron absorption performance is prepared.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of nuclear power, and particularly relates to a high-temperature-resistant yttrium-gadolinium hydride neutron moderator and a manufacturing method thereof. BACKGROUND

[0002] With the development of nuclear power technology, the working temperature of new reactors is further increased, and some technical solutions require that the neutron shielding material in the reactor can work stably at a high temperature of 600-1000 DEG C for a long time. The temperature condition has exceeded the upper limit of the use temperature of traditional neutron shielding materials such as lithium hydride and zirconium hydride. In new neutron shielding materials, yttrium hydride has a high decomposition temperature and good fast neutron moderation capacity, and is therefore considered to have good application prospects. However, the application range of yttrium hydride is restricted by the insufficient thermal neutron absorption capacity of yttrium. Gadolinium atoms have a very high thermal neutron absorption cross section, and yttrium and gadolinium have good application prospects in combination. However, there is currently a lack of effective manufacturing processes for yttrium-gadolinium composite materials, and therefore it is of high practical value to provide a manufacturing method of yttrium-gadolinium hydride neutron moderator. SUMMARY

[0003] The application aims to provide a manufacturing method of high-temperature-resistant yttrium-gadolinium hydride neutron moderator, and to manufacture shielding materials with good fast neutron moderation performance and thermal neutron absorption performance. The application also provides a high-temperature-resistant yttrium-gadolinium hydride neutron moderator.

[0004] According to an embodiment of one aspect of the application, a manufacturing method of high-temperature-resistant yttrium-gadolinium hydride neutron moderator is provided, and the method comprises the following steps:

[0005] Step a): providing yttrium powder and gadolinium powder and respectively performing pre-hydrogenation treatment, the pre-hydrogenation treatment being performed at a temperature of 200-900 DEG C and a hydrogen pressure of 0.01-0.5 MPa to obtain yttrium hydride raw powder and gadolinium hydride raw powder;

[0006] Step b): uniformly mixing the yttrium hydride raw powder and the gadolinium hydride raw powder, so that the content of Gd is 1-30% by weight, to obtain a mixed powder;

[0007] Step c): cold-pressing the mixed powder to obtain a cold-pressed body;

[0008] Step d): hydrogenation sintering the cold-pressed body at a heating temperature of 900-1400 DEG C and a hydrogen pressure of 0.05-1 MPa to obtain a high-temperature-resistant yttrium-gadolinium hydride neutron moderator.

[0009] The method can effectively manufacture the neutron shielding material with good fast neutron moderation performance and thermal neutron absorption performance, and the manufactured finished product is not prone to cracking, and the yield is high.

[0010] Further, 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 material helps to improve the uniformity of the finished product, improve the reaction efficiency, and prevent uneven hydrogenation.

[0011] Further, in some embodiments, the pre-hydrogenation time in step a) is 1-24 hours.

[0012] Further, in some embodiments, in step b), the yttrium hydride raw powder and the gadolinium hydride raw powder are mixed by using a mixer.

[0013] Further, in some embodiments, in step b), the mixing speed is 10-100 r / min, and the mixing time is 0.5-24 hours.

[0014] Further, in some embodiments, in step c), the pressure for cold pressing is 50-300 MPa, and the pressure holding time is 1-30 minutes.

[0015] Further, in some embodiments, in step d), the sintering time is 1-24 hours.

[0016] According to another aspect of the embodiments of the present application, a high-temperature-resistant yttrium-gadolinium hydride neutron moderation absorber is provided, which is manufactured by using the manufacturing method of the high-temperature-resistant yttrium-gadolinium hydride neutron moderation absorber provided in any of the preceding embodiments. The neutron moderation absorber has good fast neutron moderation performance and thermal neutron absorption performance as a neutron shielding material, and has good stability in a high-temperature environment. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 It is a finished product photo of the high-temperature-resistant yttrium-gadolinium hydride neutron moderation absorber in an embodiment;

[0018] Figure 2 It is an X-ray photo of the high-temperature-resistant yttrium-gadolinium hydride neutron moderation absorber in an embodiment;

[0019] Figure 3 It is an X-ray diffraction pattern of the high-temperature-resistant yttrium-gadolinium hydride neutron moderation absorber in an embodiment;

[0020] Figure 4 It is a high-temperature dehydrogenation curve of the high-temperature-resistant yttrium-gadolinium hydride neutron moderation absorber in an embodiment.

[0021] The purpose of the above-described drawings is to make a detailed description of the present application so that those skilled in the art can understand the technical concept of the present application, and is not intended to limit the present application. DETAILED DESCRIPTION

[0022] The present application will be further described below by specific examples in conjunction with the drawings.

[0023] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment. The appearances of the phrase "in an embodiment" in various places in the specification are not necessarily referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of one another. Those skilled in the art will appreciate that embodiments of the present application can be combined with other embodiments in their various permutations and combinations without necessarily

[0024] In the description herein, the meaning of "a plurality of" is at least two.

[0025] With the rapid development of civil nuclear power technology, in order to further improve the economic efficiency of the reactor, the working temperature of the new reactor core is also continuously increased, and in some advanced reactor design schemes, the working temperature of the neutron shielding material has reached 600-1000℃, which has reached the decomposition temperature of conventional metal hydride shielding materials such as lithium hydride and zirconium hydride. Yttrium hydride has a higher decomposition temperature and better stability at high temperatures, and also has good moderation performance for fast neutrons, so it has good application prospects as a neutron shielding material in new reactors. However, yttrium hydride itself has insufficient thermal neutron absorption capacity and is difficult to be directly applied as a neutron shielding material alone. The thermal neutron absorption cross section of gadolinium reaches 46000 barns, which is a good thermal neutron absorption material. However, mixing yttrium hydride with gadolinium can easily cause uneven mixing of materials or cracking under long-term service conditions, and there is currently a lack of effective technical solutions to prepare yttrium-gadolinium composite neutron moderators with a certain volume.

[0026] In order to overcome the above-mentioned deficiencies of the prior art, an embodiment of one aspect of the present application provides a manufacturing method of a high-temperature-resistant yttrium-gadolinium hydride neutron moderator. 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, The method comprises the following steps: Step a) providing yttrium powder and gadolinium powder and respectively performing pre-hydrogenation treatment, the pre-hydrogenation treatment being performed at a temperature of 200-900 DEG C and a hydrogen pressure of 0.01-0.5 MPa to obtain hydrogenated yttrium raw powder and hydrogenated gadolinium raw powder; Step b) uniformly mixing the hydrogenated yttrium raw powder and the hydrogenated gadolinium raw powder, the mixture having a Gd content of 1-30% by weight to obtain a mixed powder; Step c) cold-pressing the mixed powder to obtain a cold-pressed body; Step d) hydrogenation sintering the cold-pressed body at a heating temperature of 900-1400 DEG C and a hydrogen pressure of 0.05-1 MPa to obtain a high-temperature-resistant yttrium-gadolinium hydride neutron moderator and absorber.

2. The method of producing a high-temperature-resistant yttrium-gadolinium hydride neutron moderator absorber according to claim 1, characterized by, The yttrium powder and the gadolinium powder have an average particle size of 100-400 mesh.

3. The method of producing a high-temperature-resistant yttrium-gadolinium hydride neutron moderator absorber according to claim 1, characterized by, The pre-hydrogenation time in step a) is 1-24 h.

4. The method of producing a high-temperature-resistant yttrium-gadolinium hydride neutron moderator absorber according to claim 1, characterized by, In step b), a mixer is used to mix the hydrogenated yttrium raw powder and the hydrogenated gadolinium raw powder.

5. The method of producing a high-temperature-resistant yttrium-gadolinium hydride neutron moderator absorber according to claim 4, characterized by, In step b), the mixing speed is 10-100 r / min and the mixing time is 0.5-24 h.

6. The method of manufacturing a high-temperature-resistant yttrium-gadolinium hydride neutron moderator absorber according to claim 1, characterized by, In step c), the cold-pressing pressure is 50-300 MPa and the pressure holding time is 1-30 min.

7. The method of claim 1, wherein the yttrium-gadolinium hydride neutron moderator absorber is formed by a process comprising: providing a mixture of yttrium, gadolinium, and hydrogen; and heating the mixture to a temperature of about 300°C to about 400°C for a time period of about 1 hour to about 10 hours. In step d), the sintering time is 1-24 h.

8. A high temperature resistant yttrium-gadolinium hydride neutron moderator absorber, characterized in that, The high-temperature-resistant yttrium-gadolinium hydride neutron moderator and absorber is manufactured by using the manufacturing method according to any one of claims 1-7.

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