CN112851349A - Method for forming core block with hole in center - Google Patents

Method for forming core block with hole in center Download PDF

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Publication number
CN112851349A
CN112851349A CN202011625273.7A CN202011625273A CN112851349A CN 112851349 A CN112851349 A CN 112851349A CN 202011625273 A CN202011625273 A CN 202011625273A CN 112851349 A CN112851349 A CN 112851349A
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China
Prior art keywords
powder
die
center
green body
core
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Pending
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CN202011625273.7A
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Chinese (zh)
Inventor
杜江平
邹本慧
韩志华
刘文涛
李宗书
隋政
郝若彤
贾春燕
刘伟
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China North Nuclear Fuel Co Ltd
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China North Nuclear Fuel Co Ltd
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Priority to CN202011625273.7A priority Critical patent/CN112851349A/en
Publication of CN112851349A publication Critical patent/CN112851349A/en
Pending legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/51—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on compounds of actinides
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C21/00—Apparatus or processes specially adapted to the manufacture of reactors or parts thereof
    • G21C21/02—Manufacture of fuel elements or breeder elements contained in non-active casings
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/60—Aspects relating to the preparation, properties or mechanical treatment of green bodies or pre-forms
    • C04B2235/602—Making the green bodies or pre-forms by moulding
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/65—Aspects relating to heat treatments of ceramic bodies such as green ceramics or pre-sintered ceramics, e.g. burning, sintering or melting processes
    • C04B2235/656—Aspects relating to heat treatments of ceramic bodies such as green ceramics or pre-sintered ceramics, e.g. burning, sintering or melting processes characterised by specific heating conditions during heat treatment
    • C04B2235/6567—Treatment time
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/65—Aspects relating to heat treatments of ceramic bodies such as green ceramics or pre-sintered ceramics, e.g. burning, sintering or melting processes
    • C04B2235/658—Atmosphere during thermal treatment
    • C04B2235/6582—Hydrogen containing atmosphere
    • 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

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Ceramic Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
  • Materials Engineering (AREA)
  • Plasma & Fusion (AREA)
  • Structural Engineering (AREA)
  • Organic Chemistry (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Inorganic Chemistry (AREA)
  • Powder Metallurgy (AREA)

Abstract

The invention belongs to the technical field of preparation of uranium dioxide pellets, and particularly relates to a method for molding a pellet with a hole in the center. First, the UO is confirmed2The raw powder is uniform in appearance, and then UO is added2Screening raw powder to remove large-particle impurities, and mechanically mixing different batches of UO2The raw powder is homogenized to obtain powder called combined UO2Powder; will mix up UO2The powder is placed in a die and pressed into a blank, called UO2Green body, and then UO2Screening the green body to obtain powder, wherein the powder is called as granulating powder; lubricating the die by using a lubricant, wherein the lubricant is required to be uniformly coated and has consistent thickness, and the die is subjected to standing drying or slight shaking drying after coating; loading the granulated powder on a position 1/3-1/4 above a female die, and performing bidirectional compression molding on a core blank in a compression mode; demolding the core blank; threshing deviceInspecting the height and appearance of the green body after molding; placing the green body in a vacuum atmosphere sintering furnace, wherein the sintering atmosphere is wet hydrogen, and preparing to obtain the UO with the central opening2And (3) a core block. The invention can realize UO2And (4) stably molding the core blocks in batches.

Description

Method for forming core block with hole in center
Technical Field
The invention belongs to the technical field of preparation of uranium dioxide pellets, and particularly relates to a method for molding a pellet with a hole in the center.
Background
The product is designed for independent research and development, belongs to the field of the perforated uranium dioxide core block in the center of powder metallurgy process preparation, and is mainly prepared by compression molding in the preparation of the existing center perforated core block, firstly, the difficulty of the preparation technology research of the center perforated core block is that the size of the core block is small, the center hole is only about 2mm, and in the molding and demolding process, the core block is easy to generate cracks, fall corners and other defects, so that the yield is low. Second, UO for pellets2The raw powder generally has large fluctuation, and the molding process parameters need to be adjusted frequently in the pellet molding process so as to meet the molding requirements.
Disclosure of Invention
Aiming at the defects of cracks, corner drop and the like in the pellet forming process, the invention ensures the yield of the pellets by carrying out process control on the forming process; UO for pellet forming2The physical property of the raw powder fluctuates to ensure the stable preparation of the pellets in batches, and the UO is added into the pellet powder2Homogenizing the raw powder to obtain homogenized UO2The key indexes of the powder are controlled within a certain range, so that the stable maintenance of the technological parameters of the core block within a certain range in the molding process is ensured.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a method for forming a core block with a hole at the center,
1) raw material homogenization treatment: first, the UO is confirmed2Appearance of raw powderUniformly mixing, and adding UO2Screening raw powder to remove large-particle impurities, and mechanically mixing different batches of UO2The raw powder is homogenized to obtain powder called combined UO2Powder;
2) and (3) granulating powder: will mix up UO2The powder is placed in a die and pressed into a blank, called UO2Green body, and then UO2Screening the green body to obtain powder, wherein the powder is called as granulating powder;
3) die lubrication: lubricating the die by using a lubricant, wherein the lubricant is required to be uniformly coated and has consistent thickness, and the die is subjected to standing drying or slight shaking drying after coating;
4) forming a core blank: loading the granulated powder on a position 1/3-1/4 above a female die, and performing bidirectional compression molding on a core blank in a compression mode;
5) demolding the core blank; inspecting the height and appearance of the green body after demolding;
6) and (3) pellet sintering: placing the green body in a vacuum atmosphere sintering furnace, wherein the sintering atmosphere is wet hydrogen, and preparing to obtain the UO with the central opening2And (3) a core block.
Raw material homogenization treatment: UO batch2The powder is sampled and detected by adopting a 5-point sampling method, and the key parameters of the granularity, the specific surface and the loose packing density of the batch powder, which have great influence on the subsequent press-sintering process, are controlled within a certain range by adjusting mechanical mixing parameters.
And (3) granulating powder: then the UO is put2The green body was sieved using a standard sieve to obtain a powder.
Die lubrication: the lubricant components are carbon tetrachloride and zinc stearate.
Die lubrication: the lubricating part comprises the inner wall of the female die and the pressure head areas of the upper punch and the lower punch.
Forming a core blank: the pressure increasing rate and the program uniform pressure are set in the pressing process.
Demolding the core blank: in the demoulding process, when the demoulding force is lower than 100N, the female die is held by hands and is manually demoulded, and the demoulding force of the core blank is controlled by adjusting the proportion of zinc stearate and is not more than 700N.
And (3) pellet sintering: setting the high-temperature sintering temperature to 1740 +/-20 ℃ and the heat preservation time to be 4-8 h.
The beneficial effects obtained by the invention are as follows:
the UO can be realized by the preparation technical method and the process measure control of the invention2The batch stable molding of the core blocks has great significance for improving the safety of the reactor.
Detailed Description
The present invention will be described in detail with reference to specific examples.
1) Raw material homogenization treatment: first, the UO is confirmed2The raw powder is uniform in appearance, and then UO is added2Screening raw powder to remove large-particle impurities, and mechanically mixing different batches of UO2The raw powder is homogenized to obtain powder called combined UO2Powder, batch UO2The powder is sampled and detected by adopting a '5-point sampling method', and the key parameters of the particle size, the specific surface, the apparent density and the like of the powder in batch, which have great influence on the subsequent press-sintering process, are controlled within a certain range by adjusting mechanical mixing parameters.
2) And (3) granulating powder: the combined UO prepared in the step 1)2Powder is put into a die to be pressed into a blank called UO2Green body, and then UO2The green body is sieved using a standard sieve to obtain a powder of a certain particle size, which is referred to as a granulated powder.
3) Die lubrication: and lubricating the die by using a lubricant, wherein the lubricant comprises carbon tetrachloride and zinc stearate, the lubricating part comprises the inner wall of the female die and the pressure head areas of the upper punch and the lower punch, the lubricant is required to be uniformly coated and have consistent thickness, and the lubricant is subjected to standing drying or slight shaking drying after coating.
4) Forming a core blank: and 2) placing the prepared granulated powder on a position 1/3-1/4 close to a female die to reduce demoulding stroke and prevent core blocks from cracking, and in addition, in order to ensure the axial uniformity of the size of a core blank, a bidirectional pressing forming mode is adopted for pressing the core blank, and the pressing process is carried out at a set pressure-increasing rate and a program constant-speed pressing mode.
5) Core blank demolding force: in the demolding process, when the demolding force is lower than 100N, the female die is held by hands, manual demolding is carried out, the demolding force of the core blank is controlled by adjusting the proportion of zinc stearate, the demolding force is generally not more than 700N, and the height and the appearance of the green blank are inspected after demolding.
6) And (3) pellet sintering: placing the green body in a vacuum atmosphere sintering furnace, wherein the sintering atmosphere is wet hydrogen, setting the high-temperature sintering temperature to be (1740 +/-20) DEG C, and the heat preservation time to be 4-8 h, and preparing to obtain the central open pore UO with a certain size2And (3) a core block.
For 1500-2000 g of UO in different batches2Performing appearance inspection on the raw powder, removing large-particle impurities in the raw material by using a 80-mesh or 100-mesh screen, mixing for 20-30 min by using a three-dimensional mixer, sampling and detecting the granularity, specific surface and apparent density of the batch of powder by using a '5-point sampling method', ensuring that the granularity of the powder is controlled to be less than 70 micrometers and the specific surface is controlled to be 3.5-6.5 m2The apparent density is controlled to be 0.75-1.50 g/cm3；
And (3) granulating powder: the combined UO prepared in the step 1)2Putting the powder into a mold with the diameter of 40mm to be pressed into a blank, pressing the blank with the pressing force of 12T, maintaining the pressure for 10s, weighing and then adding UO2Sieving the green body by a standard sieve of 40 meshes, and taking powder below 40 meshes as granulating powder.
Die lubrication: and (2) lubricating the die by using a lubricant, wherein the lubricant comprises carbon tetrachloride and zinc stearate (25 ml of carbon tetrachloride is (0.7-1) g of zinc stearate), the lubricating part comprises the inner wall of the female die and the pressure head areas of the upper punch and the lower punch, the lubricant is required to be uniformly coated and have consistent thickness, and the lubricant is subjected to standing drying or slight shaking drying after coating.
And (3) taking 1.5-2.0 g of the granulated powder obtained in the step 2), filling the powder into a mold with a designed size, wherein the filling position is close to 1/3 parts of the female mold, the pressing mode is bidirectional pressing, the pressing pressure is 5-8 KN, and the pressure is maintained for 10 s.
When demoulding, if the demoulding force is more than 700N, the zinc stearate is added to ensure that the demoulding force is less than or equal to 700N for demoulding, and when the demoulding force is less than 100N, the female die is held by hand and is manually demoulded to obtain UO2And (4) green pressing.
For UO2Inspecting the appearance and height of the green body, controlling the height to be 8-11 mm,if the appearance has defects such as cracks, falling blocks and the like, the defects need to be removed in time;
mixing UO2Placing the green body in a vacuum atmosphere sintering furnace, setting the sintering atmosphere to be wet hydrogen, setting the high-temperature sintering temperature to be 1700-1770 ℃ and the heat preservation time to be 4h, and preparing to obtain the UO with the central opening2And (3) a core block.
With UO2The raw powder is used as a raw material, and through homogenization treatment, granulation, forming process control and sintering, the UO with a central opening can be realized2The batch stable preparation of the core block has great significance for improving the safety of the reactor.

Claims (8)

1. A method for forming a core block with a hole in the center is characterized in that:
1) raw material homogenization treatment: first, the UO is confirmed2The raw powder is uniform in appearance, and then UO is added2Screening raw powder to remove large-particle impurities, and mechanically mixing different batches of UO2The raw powder is homogenized to obtain powder called combined UO2Powder;
2) and (3) granulating powder: will mix up UO2The powder is placed in a die and pressed into a blank, called UO2Green body, and then UO2Screening the green body to obtain powder, wherein the powder is called as granulating powder;
3) die lubrication: lubricating the die by using a lubricant, wherein the lubricant is required to be uniformly coated and has consistent thickness, and the die is subjected to standing drying or slight shaking drying after coating;
4) forming a core blank: loading the granulated powder on a position 1/3-1/4 above a female die, and performing bidirectional compression molding on a core blank in a compression mode;
5) demolding the core blank; inspecting the height and appearance of the green body after demolding;
6) and (3) pellet sintering: placing the green body in a vacuum atmosphere sintering furnace, wherein the sintering atmosphere is wet hydrogen, and preparing to obtain the UO with the central opening2And (3) a core block.
2. The center-holed pellet molding method according to claim 1, characterized in that: raw material homogenization treatment: UO batch2The powder is taken by a 5-point sampling methodAnd (4) performing sampling detection, and controlling key parameters of the particle size, the specific surface and the loose packing density of the batch powder, which have great influence on the subsequent press-sintering process, within a certain range by adjusting mechanical mixing parameters.
3. The center-holed pellet molding method according to claim 1, characterized in that: and (3) granulating powder: then the UO is put2The green body was sieved using a standard sieve to obtain a powder.
4. The center-holed pellet molding method according to claim 1, characterized in that: die lubrication: the lubricant components are carbon tetrachloride and zinc stearate.
5. The center-holed pellet molding method according to claim 1, characterized in that: die lubrication: the lubricating part comprises the inner wall of the female die and the pressure head areas of the upper punch and the lower punch.
6. The center-holed pellet molding method according to claim 1, characterized in that: forming a core blank: the pressure increasing rate and the program uniform pressure are set in the pressing process.
7. The center-holed pellet molding method according to claim 4, wherein: demolding the core blank: in the demoulding process, when the demoulding force is lower than 100N, the female die is held by hands and is manually demoulded, and the demoulding force of the core blank is controlled by adjusting the proportion of zinc stearate and is not more than 700N.
8. The center-holed pellet molding method according to claim 1, characterized in that: and (3) pellet sintering: setting the high-temperature sintering temperature to 1740 +/-20 ℃ and the heat preservation time to be 4-8 h.
CN202011625273.7A 2020-12-31 2020-12-31 Method for forming core block with hole in center Pending CN112851349A (en)

Priority Applications (1)

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CN202011625273.7A CN112851349A (en) 2020-12-31 2020-12-31 Method for forming core block with hole in center

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Application Number Priority Date Filing Date Title
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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100855108B1 (en) * 2007-03-09 2008-08-29 한국원자력연구원 Method of manufacturing u3o8 powder and method of manufacturing uo2 fuel pellets using the same
CN104446478A (en) * 2013-09-24 2015-03-25 中核北方核燃料元件有限公司 Method for preparing thorium dioxide pellets
CN105788685A (en) * 2014-12-26 2016-07-20 中核北方核燃料元件有限公司 Method for preparing annular uranium dioxide pellet
CN106653126A (en) * 2016-12-28 2017-05-10 中核北方核燃料元件有限公司 Method and mould for preparing annular UO2 fuel pellet
CN108695008A (en) * 2017-04-07 2018-10-23 中核北方核燃料元件有限公司 A kind of low micro- heap UO of denseization2The automatic forming method of fuel pellet green compact

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100855108B1 (en) * 2007-03-09 2008-08-29 한국원자력연구원 Method of manufacturing u3o8 powder and method of manufacturing uo2 fuel pellets using the same
CN104446478A (en) * 2013-09-24 2015-03-25 中核北方核燃料元件有限公司 Method for preparing thorium dioxide pellets
CN105788685A (en) * 2014-12-26 2016-07-20 中核北方核燃料元件有限公司 Method for preparing annular uranium dioxide pellet
CN106653126A (en) * 2016-12-28 2017-05-10 中核北方核燃料元件有限公司 Method and mould for preparing annular UO2 fuel pellet
CN108695008A (en) * 2017-04-07 2018-10-23 中核北方核燃料元件有限公司 A kind of low micro- heap UO of denseization2The automatic forming method of fuel pellet green compact

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
伍志明: ""二氧化铀核燃料的粉末冶金技术"", 《粉末冶金技术》 *
畅欣等: "《压水堆燃料元件制造文集》", 31 March 2005, 原子能出版社 *

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