CN117238538A - Manufacturing method of uranium nitride fuel pellets - Google Patents
Manufacturing method of uranium nitride fuel pellets Download PDFInfo
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- CN117238538A CN117238538A CN202311235205.3A CN202311235205A CN117238538A CN 117238538 A CN117238538 A CN 117238538A CN 202311235205 A CN202311235205 A CN 202311235205A CN 117238538 A CN117238538 A CN 117238538A
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- uranium nitride
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- MVXWAZXVYXTENN-UHFFFAOYSA-N azanylidyneuranium Chemical compound [U]#N MVXWAZXVYXTENN-UHFFFAOYSA-N 0.000 title claims abstract description 70
- 239000008188 pellet Substances 0.000 title claims abstract description 39
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 24
- 239000000446 fuel Substances 0.000 title description 14
- 238000005245 sintering Methods 0.000 claims abstract description 66
- 229910052770 Uranium Inorganic materials 0.000 claims abstract description 50
- 239000000843 powder Substances 0.000 claims abstract description 49
- JFALSRSLKYAFGM-UHFFFAOYSA-N uranium(0) Chemical compound [U] JFALSRSLKYAFGM-UHFFFAOYSA-N 0.000 claims abstract description 47
- 238000000034 method Methods 0.000 claims abstract description 16
- 238000005121 nitriding Methods 0.000 claims abstract description 13
- 239000011812 mixed powder Substances 0.000 claims abstract description 11
- 238000002844 melting Methods 0.000 claims abstract description 9
- 230000008018 melting Effects 0.000 claims abstract description 9
- 229910000711 U alloy Inorganic materials 0.000 claims abstract description 6
- 238000005984 hydrogenation reaction Methods 0.000 claims abstract description 6
- 150000001875 compounds Chemical class 0.000 claims abstract description 5
- 238000006356 dehydrogenation reaction Methods 0.000 claims abstract description 4
- 239000002243 precursor Substances 0.000 claims description 19
- 238000002156 mixing Methods 0.000 claims description 18
- 229910052751 metal Inorganic materials 0.000 claims description 17
- 239000002184 metal Substances 0.000 claims description 17
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 16
- 238000010438 heat treatment Methods 0.000 claims description 16
- 239000011230 binding agent Substances 0.000 claims description 15
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 14
- 239000012298 atmosphere Substances 0.000 claims description 14
- 239000002202 Polyethylene glycol Substances 0.000 claims description 13
- 229920001223 polyethylene glycol Polymers 0.000 claims description 13
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 12
- 239000000203 mixture Substances 0.000 claims description 10
- 229910052786 argon Inorganic materials 0.000 claims description 8
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 8
- 239000001301 oxygen Substances 0.000 claims description 8
- 229910052760 oxygen Inorganic materials 0.000 claims description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 8
- 238000000498 ball milling Methods 0.000 claims description 6
- 229910052757 nitrogen Inorganic materials 0.000 claims description 6
- 239000004372 Polyvinyl alcohol Substances 0.000 claims description 5
- 229920002451 polyvinyl alcohol Polymers 0.000 claims description 5
- 238000003825 pressing Methods 0.000 claims description 5
- 239000007789 gas Substances 0.000 claims description 4
- 238000011282 treatment Methods 0.000 claims description 3
- 238000000748 compression moulding Methods 0.000 abstract 1
- 239000002245 particle Substances 0.000 description 9
- 238000005406 washing Methods 0.000 description 6
- 239000007791 liquid phase Substances 0.000 description 5
- 238000002360 preparation method Methods 0.000 description 5
- 230000001681 protective effect Effects 0.000 description 5
- 230000004927 fusion Effects 0.000 description 4
- 239000001257 hydrogen Substances 0.000 description 4
- 229910052739 hydrogen Inorganic materials 0.000 description 4
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 3
- 239000002253 acid Substances 0.000 description 3
- 239000012300 argon atmosphere Substances 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 238000000354 decomposition reaction Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 150000002431 hydrogen Chemical class 0.000 description 3
- 229910017604 nitric acid Inorganic materials 0.000 description 3
- OOAWCECZEHPMBX-UHFFFAOYSA-N oxygen(2-);uranium(4+) Chemical compound [O-2].[O-2].[U+4] OOAWCECZEHPMBX-UHFFFAOYSA-N 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- FCTBKIHDJGHPPO-UHFFFAOYSA-N uranium dioxide Inorganic materials O=[U]=O FCTBKIHDJGHPPO-UHFFFAOYSA-N 0.000 description 3
- -1 uranium nitrides Chemical class 0.000 description 3
- 239000004743 Polypropylene Substances 0.000 description 2
- 239000000306 component Substances 0.000 description 2
- 238000005520 cutting process Methods 0.000 description 2
- 238000011049 filling Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000003758 nuclear fuel Substances 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 229920001155 polypropylene Polymers 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910001093 Zr alloy Inorganic materials 0.000 description 1
- 239000012752 auxiliary agent Substances 0.000 description 1
- 238000010923 batch production Methods 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 229910010293 ceramic material Inorganic materials 0.000 description 1
- 239000008358 core component Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 235000019441 ethanol Nutrition 0.000 description 1
- 230000004992 fission Effects 0.000 description 1
- 239000002816 fuel additive Substances 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 238000011031 large-scale manufacturing process Methods 0.000 description 1
- 229910001338 liquidmetal Inorganic materials 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 229940095674 pellet product Drugs 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 238000007873 sieving Methods 0.000 description 1
- 238000002490 spark plasma sintering Methods 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- NBWXXYPQEPQUSB-UHFFFAOYSA-N uranium zirconium Chemical compound [Zr].[Zr].[U] NBWXXYPQEPQUSB-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
- Y02E30/30—Nuclear fission reactors
Landscapes
- Inorganic Compounds Of Heavy Metals (AREA)
Abstract
A method for manufacturing uranium nitride pellets, comprising the steps of: the method comprises the steps of preparing uranium powder by hydrogenation and dehydrogenation of metallic uranium, nitriding and denitrifying the uranium powder to prepare mixed powder of UN and U2N3, adding pure uranium, uranium alloy or uranium-containing compound with melting point lower than 1700 ℃ into the mixed powder as a sintering aid, and sintering at 1700-1950 ℃ after compression molding to obtain uranium nitride pellets. By adopting the method, effective sintering of uranium nitride can be realized under normal pressure, a compact uranium nitride core block is obtained, and the manufacturing process of the uranium nitride core block is simplified.
Description
Technical Field
The invention belongs to the field of nuclear power, and particularly relates to a manufacturing method of uranium nitride fuel pellets.
Background
After the accident of the japan foolish nuclear power station in 2011, the safety performance of the commercial light water reactor nuclear power station, in particular, the safety performance of the core components of the reactor such as the fuel pellets, is highly concerned. At present, a light water reactor nuclear power station in operation still commonly adopts uranium dioxide as a fuel pellet, and the uranium dioxide has the advantages of good chemical stability, high melting point and the like; however, the ceramic material has low density and poor heat conduction performance, so that the burning depth is low, the processing size is limited, and particularly, due to the limitation of the heat conduction performance, a long time is required to cool to a safe temperature when an emergency shutdown is required in the event of an accident. Therefore, uranium Nitride (UN) pellets with higher uranium density and better heat conduction property become a popular candidate material for new generation nuclear fuels. The UN powder has high chemical activity, an oxide film is easy to form on the surface, and the powder is difficult to be fully fused with the direct sintering powder, so that the density of the sintered body is too low. The existing technology needs to sinter under high pressure or to improve the effective sintering of uranium nitride pellets in a high-purity protective gas atmosphere with strictly controlled oxygen removal, and has high cost, high technical difficulty and difficulty in realizing large-scale production. Therefore, the method for manufacturing the uranium nitride fuel pellets under normal pressure has high value for promoting popularization and application of the uranium nitride pellets.
Disclosure of Invention
The invention aims to provide a manufacturing method of uranium nitride fuel pellets, which realizes the sintering manufacture of uranium nitride pellets under normal pressure.
According to an embodiment of the present invention, there is provided a uranium nitride pellet manufacturing method including the steps of: providing a metal uranium ingot, and adding hydrogen into the metal uranium ingotCarrying out multiple hydrogenation and dehydrogenation treatments in a chemical furnace, and ball milling to obtain uranium powder; putting the uranium powder into a nitriding furnace for nitriding to obtain U 2 N 3 A powder; heating part U in denitrification furnace 2 N 3 Decomposing the powder to obtain UN and U 2 N 3 Mixing the powder; combining the UN with U 2 N 3 Mixing and adding a sintering aid, and mixing and pressing to obtain a sintering precursor, wherein the sintering aid is pure uranium, uranium alloy or uranium-containing compound with a melting point lower than 1700 ℃; and sintering the sintering precursor at 1700-1950 ℃ to obtain the uranium nitride core block.
By adding pure uranium, uranium alloy or uranium-containing compound with low melting point, liquid phase can be formed at lower temperature, and diffusion among UN particles and neck growth are promoted, so that the density and mechanical property of the pellet are improved.
Further, in some embodiments, the sintering aid is added in an amount of 1% -15% by weight.
Further, in some embodiments, the sintering precursor is sintered under vacuum or an inert atmosphere. The sintering process should avoid oxidation of the powder as much as possible, so that the powder should be protected by vacuum or inert atmosphere.
Further, in some embodiments, the inert atmosphere comprises nitrogen or argon. Since only UN in uranium nitrides is stable at sintering temperature, U 2 N 3 Decomposition occurs, so nitrogen can be used as a protective atmosphere.
Further, in some embodiments, the sintering aid comprises U 3 Si 2 Or pure U. U (U) 3 Si 2 Is 1662 ℃ and pure U is 1138 ℃ and can form liquid phase under sintering condition to eliminate UO 2 Is a negative effect of (2); meanwhile, the components of the fuel additive remain in the sintered finished pellets without negatively affecting the fuel performance.
Further, in some embodiments, the sintering aid may have a pure U content of 0-10% by weight.
Further, in some embodiments, the UN is combined with the U in the following steps 2 N 3 The operation of mixing the mixed powder and the sintering aid is carried out under the protection of an argon atmosphere, and the water vapor and oxygen content in the atmosphere are controlled to be less than 0.1ppm. During the mixing process, the contact between the powder and oxygen should be reduced as much as possible, and the oxidation of UN should be reduced.
Further, the sintering precursor is pressed for more than 20 seconds under the pressure of not less than 100 MPa.
Further, prior to pressing the sintering precursor, further comprising feeding the UN and U 2 N 3 And adding a binder to the mixture of the mixed powder and the sintering aid. The binder can enhance structural stability of the sintered precursor while improving flowability of the powder during compacting, thereby achieving higher compacted density.
Further, in some embodiments, the binder is configured as an absolute ethanol solution of polyethylene glycol or polyvinyl alcohol, and the polyethylene glycol or polyvinyl alcohol is added in an amount of not more than 0.5% by weight.
Further, in some embodiments, UN and U are combined prior to adding the sintering aid 2 N 3 The mixing ratio of (C) is U 2 N 3 Accounting for 5 to 15 percent of the weight ratio. U (U) 2 N 3 The sintering activity is higher, and the fusion among powder particles can be promoted in the sintering process, so that the density of a finished pellet product is improved; but U is 2 N 3 During sintering, the mixture is decomposed to generate gas, and excessive addition can cause defects such as air holes.
Drawings
FIG. 1 is a schematic flow chart of manufacturing uranium nitride pellets according to an embodiment.
The above-described drawings are intended to explain the present invention in detail with the accompanying drawings so that those skilled in the art can understand the technical concept of the present invention, and are not intended to limit the present invention.
Detailed Description
The invention will now be described in further detail with reference to the accompanying drawings by means of specific examples.
Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment herein. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments limited to the same embodiment. Those skilled in the art will appreciate that embodiments herein may be combined with other embodiments without structural conflict. In the description herein, the meaning of "plurality" is at least two.
The high uranium density fuel pellets are of great significance for economic sustainability and safety improvement of commercial light water stacks. Compared with uranium dioxide pellets, uranium nitride has the advantages of high heat conduction and high uranium density, and meanwhile, the advantages of high melting point, low thermal expansion, radiation resistance, low release rate of fission gas, good compatibility with liquid metal and the like of ceramic uranium materials are maintained. Therefore, the uranium nitride in the nuclear fuel pellets of the new generation has good application prospect. However, the existing uranium nitride pellet preparation process is still not mature, and is usually required to be manufactured by adopting complicated processes such as high-pressure sintering, spark plasma sintering and the like, and the processes have high requirements on equipment, so that small-batch preparation on a laboratory scale can be realized, and batch production of uranium nitride is not facilitated.
In order to solve the problems, the embodiment of the invention provides a uranium nitride manufacturing process, which can realize effective sintering of uranium nitride under normal pressure conditions to prepare uranium nitride pellets with higher density. The method specifically comprises the following steps:
firstly, providing a metal uranium ingot, putting the metal uranium ingot into a hydrogenation furnace for multiple hydrogenation and dehydrogenation treatments, ball milling and sieving to obtain uranium powder. Then, the powder is put into a nitriding furnace for nitriding, ball-milled and sieved to obtain U 2 N 3 And (3) powder. For at least part of U in denitrification furnace 2 N 3 Further heating to make U 2 N 3 Decomposing to obtain UN powder. UN is combined with U in a tightly controlled oxygen environment (in some preferred embodiments, configured as a vacuum environment or a protective atmosphere of argon/nitrogen) 2 N 3 Mixing with sintering aid, and pressing into cake-shaped sintering precursor. In a preferred embodiment, the pressing pressure is not less than 100MPa,the dwell time is not less than 20s. Wherein the sintering aid adopts pure uranium, uranium alloy or uranium-containing compound with melting point lower than 1700 ℃. In the preferred embodiment, the sintering aid is added in an amount of 1wt% to 5wt% and no more than 10wt% pure uranium and U are selected 3 Si 2 Mixing the powder, and adding polyethylene glycol or polypropylene from absolute ethanol solution as binder, wherein the addition amount of polyethylene glycol or polypropylene is not more than 0.5wt%. Finally, sintering the sintering precursor into a finished product of uranium nitride pellets at 1700-1950 ℃.
By the method, the effective sintering of the uranium nitride fuel pellets can be realized under normal pressure, and the compact uranium nitride fuel pellets can be prepared.
In a preferred embodiment, the specific process for manufacturing uranium nitride fuel pellets is as follows, as shown in fig. 1:
firstly, performing step 1, namely taking a metal uranium ingot, processing the metal uranium ingot into a sheet with the thickness of about 5mm, immersing and washing the sheet by using 50vol% nitric acid, removing a surface oxide film, and washing residual acid liquor by using absolute ethyl alcohol.
And next, carrying out step 2, namely putting the metal uranium sheet into a tube furnace, introducing hydrogen, heating to 200 ℃, preserving heat and hydrogenating, further heating to 600 ℃ and dehydrogenating, and repeating the steps for 2-3 times to crush the uranium sheet into uranium powder.
Next, step 3 is carried out, uranium powder is ball-milled and sieved, and is put into a nitriding furnace to be heated to 500 ℃ for nitriding, thus obtaining U 2 N 3 And (3) powder.
Next, step 4 is performed to divide U into portions 2 N 3 The powder was heated to 1300 ℃ and incubated for 2h to decompose it into UN powder.
Next, go to step 5, combine UN with U 2 N 3 The powders were mixed in a weight ratio of 9:1, to which 10wt% of U was added 3 Si 2 The powder is used as a sintering aid and ball-milled for 48 hours under the protection of argon. The water vapor and oxygen content in the protective atmosphere is controlled to be less than 0.1ppm.
Next, step 6 is performed, in which polyethylene glycol is dissolved in absolute ethanol to prepare a binder solution with the concentration of 2wt%, the binder solution is mixed in the powder mixture after ball milling, the polyethylene glycol content is controlled to be 0.2wt%, and the mixture is dried after uniform mixing to evaporate the absolute ethanol.
Subsequently, step 7 was performed, the above mixture was charged into a mold, and the pressure was maintained at 200MPa for 30s using a biaxial hydraulic press, and the block-shaped sintered precursor was obtained by demolding.
And finally, transferring the sintering precursor into an atmosphere sintering furnace, introducing argon for protection, heating to 600 ℃ at a speed of 5 ℃/min, and preserving heat for 1h to enable polyethylene glycol to be fully decomposed, gasified and escaped. Continuously heating to 1800 ℃, preserving heat for 1.5h to finish sintering, and U is at the temperature 2 N 3 Completely decompose into UN, U 3 Si 2 Melt to a liquid phase and promote fusion of the UN particles. And then cooling to room temperature at a speed of 10 ℃/min to finish sintering preparation of the uranium nitride core block, and obtaining a core block finished product with the density of not less than 80% T.D. wherein T.D. is the theoretical density.
In another preferred embodiment of the invention, the uranium nitride fuel pellets are manufactured as follows:
firstly, carrying out step 1, namely taking a metal uranium ingot, cutting the metal uranium ingot into particles with the side length not exceeding 5mm, immersing and washing the particles by using 50vol% of nitric acid, removing a surface oxide film, and washing residual acid liquor by using absolute ethyl alcohol.
And next, carrying out step 2, namely putting the metal uranium particles into a tube furnace, introducing hydrogen, heating to 200 ℃, preserving heat and hydrogenating, further heating to 600 ℃ and dehydrogenating, and repeating the steps for 2-3 times to crush the metal uranium particles into uranium powder.
Next, step 3 is carried out, uranium powder is ball-milled and sieved, and is put into a nitriding furnace to be heated to 500 ℃ for nitriding, thus obtaining U 2 N 3 And (3) powder.
Next, step 4 is performed to convert U 2 N 3 Heating the powder to 1300 ℃ and preserving heat to enable part of U 2 N 3 Decomposition to UN, U was detected by measuring the total weight of the powder 2 N 3 Decomposition rate of (C) until UN and U are obtained 2 N 3 Mixing the mixed powder in a mixing ratio of 19:1.
Next, step 5 is performed to purify the mixture in an isolation box protected by argon atmosphereUranium powder and U 3 Si 2 Mixing the powder according to the weight ratio of 1:9, and adding the powder as a sintering aid into UN and U 2 N 3 The addition amount of the sintering aid was controlled to 5wt%. Under the protection of argon atmosphere, adding the UN and the U of the sintering auxiliary agent 2 N 3 The mixed powder was ball-milled in a ball mill for 48 hours. The water vapor and oxygen content in the argon atmosphere is controlled to be lower than 0.1ppm.
Next, step 6 is performed, in which a binder is added to the mixed powder subjected to ball milling. The binder adopts an absolute ethanol solution of polyvinyl alcohol with the concentration of 2wt percent, and the addition amount of the binder is controlled to be 0.5wt percent. And (3) uniformly stirring the binder and the mixed powder, and drying to evaporate the ethanol.
And 7, filling the mixed powder added with the binder into a die, maintaining the pressure for 20s under 400MPa by using a biaxial hydraulic press, and demolding to obtain a massive sintering precursor.
And finally, transferring the sintering precursor into a nitrogen sintering furnace, filling nitrogen for atmosphere protection, heating to 600 ℃ at a speed of 5 ℃/min, and preserving heat for 1h to enable polyethylene glycol to be fully decomposed, gasified and escaped. Continuously heating to 1800 ℃, preserving heat for 1.5h to finish sintering, and U is at the temperature 2 N 3 Completely decomposed into UN, metals U and U 3 Si 2 Melt to a liquid phase and promote fusion of the UN particles. And then cooling to room temperature at a speed of 10 ℃/min to finish sintering preparation of the uranium nitride core block, and obtaining a core block finished product with the density of not less than 80% T.D. wherein T.D. is the theoretical density.
In yet another preferred embodiment of the present invention, the specific process for manufacturing uranium nitride fuel pellets is as follows:
firstly, performing step 1, namely taking a metal uranium ingot, cutting the metal uranium ingot into slices with the thickness of 2.5mm, immersing and washing the slices by using 50% vol nitric acid, removing a surface oxide film, and washing residual acid liquor by using absolute ethyl alcohol.
And next, carrying out step 2, namely putting the metal uranium sheet into a tube furnace, introducing hydrogen, heating to 200 ℃, preserving heat and hydrogenating, further heating to 600 ℃ and dehydrogenating, and repeating the steps for 2-3 times to crush the uranium sheet into uranium powder.
Next, step 3 is carried out, uranium powder is ball-milled and sieved, and is put into a nitriding furnace to be heated to 500 ℃ for nitriding, thus obtaining U 2 N 3 And (3) powder.
Next, step 4 is performed to divide U into portions 2 N 3 The powder was heated to 1300 ℃ and incubated for 2h to decompose it into UN powder.
Next, go to step 5, combine UN with U 2 N 3 Powder mixing to give U 2 N 3 15% by weight of U is added thereto, and 15% by weight of U is added thereto 3 Si 2 The powder was ball milled for 48h under argon protection. The water vapor and oxygen content in the protective atmosphere is controlled to be less than 0.1ppm.
Next, step 6 is performed, in which polyethylene glycol is dissolved in absolute ethanol to prepare a binder solution with the concentration of 2wt%, the binder solution is mixed in the powder mixture after ball milling, the polyethylene glycol content is controlled to be 0.2wt%, and the mixture is dried after uniform mixing to evaporate the absolute ethanol.
Subsequently, step 7 is carried out, the mixture is added into a die, the pressure is maintained for 60s under 100MPa by using a biaxial hydraulic press, and the die is removed to obtain a massive sintered precursor.
And finally, transferring the sintering precursor into a vacuum sintering furnace, vacuumizing to below 0.1Pa, heating to 600 ℃ at a speed of 5 ℃/min, and preserving heat for 1h to enable polyethylene glycol to be fully decomposed, gasified and escaped. Continuously heating to 1800 ℃, preserving heat for 1.5h to finish sintering, and U is at the temperature 2 N 3 Completely decompose into UN, U 3 Si 2 Melt to a liquid phase and promote fusion of the UN particles. And then cooling to room temperature at a speed of 10 ℃/min to finish sintering preparation of the uranium nitride core block, and obtaining a core block finished product with the density of not less than 80% T.D. wherein T.D. is the theoretical density.
In other embodiments, the sintering aid may also be a low melting uranium alloy, such as a uranium zirconium alloy having a melting point of 1160 ℃.
The above-described embodiments are intended to provide further detailed description of the present invention so that those skilled in the art can understand the technical concept of the present invention. Within the scope of the claims, the components or method steps involved are optimized or replaced equivalently, and the implementation manners of the different embodiments are combined without any occurrence of principle conflict, which falls within the scope of protection of the present invention.
Claims (11)
1. A method for manufacturing uranium nitride pellets, comprising the steps of:
providing a metal uranium ingot, putting the metal uranium ingot into a hydrogenation furnace for multiple hydrogenation and dehydrogenation treatments, and ball milling to obtain uranium powder;
putting the uranium powder into a nitriding furnace for nitriding to obtain U 2 N 3 A powder;
heating part U in denitrification furnace 2 N 3 Decomposing the powder to obtain UN powder;
combining the UN with U 2 N 3 Mixing and adding a sintering aid, and mixing and pressing to obtain a sintering precursor, wherein the sintering aid is pure uranium, uranium alloy or uranium-containing compound with a melting point lower than 1700 ℃;
and sintering the sintering precursor at 1700-1950 ℃ to obtain the uranium nitride core block.
2. The method of manufacturing uranium nitride pellets according to claim 1, wherein the sintering aid is added in an amount of 1% -15% by weight.
3. A method of manufacturing uranium nitride pellets according to claim 1 or claim 2, wherein the sintering precursor is sintered under vacuum or an inert atmosphere.
4. A method of manufacturing uranium nitride pellets according to claim 3, wherein the inert atmosphere includes nitrogen or argon.
5. A method of manufacturing uranium nitride pellets according to claim 1 or claim 2, wherein the sintering aid comprises U 3 Si 2 Or pure U.
6. The method for manufacturing uranium nitride pellets according to claim 5, wherein the content of pure U in the sintering aid is 0 to 10% by weight.
7. A method of manufacturing uranium nitride pellets according to claim 1 or claim 2, wherein, in combining the UN with U 2 N 3 The operation of mixing the mixed powder and the sintering aid is carried out under the protection of argon gas, and the water vapor and oxygen content in the atmosphere are controlled to be less than 0.1ppm.
8. The method for producing uranium nitride pellets according to claim 1 or 2, wherein the sintered precursor is pressed at a pressure of not less than 100MPa for 20s or more.
9. The method of manufacturing uranium nitride pellets according to claim 1 or 2, further comprising, prior to compacting the sintering precursor, directing the UN and U towards each other 2 N 3 And adding a binder to the mixture of the mixed powder and the sintering aid.
10. The method of manufacturing uranium nitride pellets according to claim 9, wherein the binder is configured as an absolute ethanol solution of polyethylene glycol or polyvinyl alcohol, and the polyethylene glycol or polyvinyl alcohol is added in an amount of not more than 0.5% by weight.
11. A method of manufacturing uranium nitride pellets according to claim 1 or claim 2, characterised in that UN and U are prior to adding the sintering aid 2 N 3 The mixing ratio of (C) is U 2 N 3 Accounting for 5 to 15 percent of the weight ratio.
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