CN109994235B - Preparation method of UO2 fuel pellet - Google Patents

Preparation method of UO2 fuel pellet Download PDF

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Publication number
CN109994235B
CN109994235B CN201711471660.8A CN201711471660A CN109994235B CN 109994235 B CN109994235 B CN 109994235B CN 201711471660 A CN201711471660 A CN 201711471660A CN 109994235 B CN109994235 B CN 109994235B
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China
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temperature
paraffin
sintering
powder
degreasing
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CN109994235A (en
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张翔
潘小强
杨静
许奎
张雨
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Nuclear Power Institute of China
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Nuclear Power Institute of China
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    • 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
    • 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

Abstract

The invention belongs to the technical field of nuclear fuel manufacturing, and particularly relates to a preparation method of UO2 fuel pellets. The invention comprises the following steps: step 1, preparing a feed; step 2, injection molding process; step 3, solvent degreasing; and 4, degreasing and sintering. The invention can realize the high-efficiency near-net forming of the fuel pellet, reduce the cost, obtain uniform density, high dimensional precision and surface smoothness, and be flexibly applied to the design research of new fuels.

Description

Preparation method of UO2 fuel pellet
Technical Field
The invention belongs to the technical field of nuclear fuel manufacturing, and particularly relates to a preparation method of UO2 fuel pellets.
Background
At present UO2The fuel pellets are generally prepared by powder metallurgy by mixing UO2Screening powder, pressing, forming, sintering, and grinding to obtain pellet. However, when the UO2 fuel pellet is faced with a new design shape or is hollow, the pellet obtained by the press forming has large processing amount and high pellet processing cost, and the pellet is fragile when the pellet is processed at a tip or a thin part, thereby seriously influencing the efficiency of production and research.
The ceramic injection molding combines the plastic injection molding and the powder metallurgy technology, the injection molding realizes the coating of polymer powder particles after the ceramic powder is mixed with a polymer binder, the polymer coated powder particles have good rheological property at the injection temperature and under the injection pressure, a mold is filled to obtain an injection green body with a specific shape, and the injection green body is degreased and sintered by heating or other physical and chemical methods to obtain a compact ceramic part with required appearance shape, size precision and microstructure.
Disclosure of Invention
The technical problems solved by the invention are as follows: the invention provides a preparation method of UO2 fuel pellet, which can realize high-efficiency near-net forming of the fuel pellet, reduce cost, obtain uniform density, high dimensional precision and surface smoothness, and be flexibly applied to new fuel design research.
The technical scheme adopted by the invention is as follows:
a preparation method of UO2 fuel pellets comprises the following steps:
step 1, preparing a feed; step 2, injection molding process; step 3, solvent degreasing; and 4, degreasing and sintering.
The specific steps of the step 1 are as follows: reducing the treated UO2Sieving the powder, keeping the temperature at 170 ℃, adding polystyrene and polypropylene, then paraffin and stearic acid to an internal mixer, and finally adding UO2Powder until the mixing is finished.
The specific steps of the step 2 are as follows: after granulation in step 1, injection is carried out on an injection molding machine to obtain hollow UO2The green body was injected.
The specific steps of the step 3 are as follows: mixing UO2The injection green bodies were solvent degreased in flowing dichloromethane to remove a portion of the paraffin.
The specific steps of the step 4 are as follows: after removing part of paraffin, directly carrying out thermal degreasing and sintering in a de-sintering integrated furnace, wherein Ar + 5% H is kept in the de-sintering integrated process2The temperature of the hollow UO is kept at 300 ℃ and 1000 ℃ for 1-2h respectively, then the temperature is slowly increased to 1650-1750 ℃ and kept at 2-4h, the temperature is slowly decreased to 900 ℃ and then the hollow UO is cooled along with the furnace to obtain the sintered hollow UO2And (3) a core block.
The UO2The particle size of the powder is 10-200 μm; the adhesive adopts a polypropylene-paraffin-polystyrene-stearic acid system, wherein the mass fraction of polypropylene in the adhesive is 30-40%, the mass fraction of paraffin is 35-45%, the mass fraction of polystyrene is 15-25%, and the mass fraction of stearic acid is 2-10%; the UO2 powder loading in the feed was: 48-55 vol%.
The injection temperature is 190 ℃ and 220 ℃, and the injection pressure is 60-90 MPa.
The temperature of the dichloromethane is 35-37 ℃.
The invention has the beneficial effects that:
the UO2 fuel pellet preparation method provided by the invention can be used for preparing UO with complex shape or hollow2The density of the core block after sintering reaches over 96 percent T.D., the surface finish is good, and the core block conforms to UO2Index requirements of the pellets.
For UOs of hollow or replicated geometry2Preparation of pellets, phase transferThe traditional pressing and sintering process has the advantages of high forming efficiency of the injection forming process, less grinding processing amount, high precision, low comprehensive cost, stronger flexibility and obvious advantages.
Detailed Description
The method for preparing UO2 fuel pellets according to the present invention will be described in further detail with reference to the following specific examples.
Example 1
The preparation method of UO2 fuel pellet provided by this embodiment includes the following steps:
step 1, preparation of feedstock
Firstly, reducing the treated UO2Sieving the powder to obtain powder with the particle size of 10-200 mu m, wherein the binder adopts a polypropylene-paraffin-polystyrene-stearic acid system, the loading amount of the powder in the feed is 48 vol%, and the proportion of the binder is selected as follows: polypropylene PP (30%) + paraffin PW (35%) + polystyrene PS (25%) + stearic acid SA (10%). The preparation of the feedstock is carried out in an internal mixer, polystyrene and polypropylene, then paraffin and stearic acid are added at a temperature of about 170 ℃, and finally UO is added2Powder until the mixing is finished.
Step 2, injection molding process
Granulating the banburying feed, injecting on an injection molding machine, adjusting injection temperature (190-2The green body was injected.
Step 3, solvent degreasing
Mixing UO2The injection green bodies were solvent degreased in flowing dichloromethane maintaining a solvent temperature of 35 ℃.
Step 4, degreasing and sintering
After removing part of paraffin, directly carrying out thermal degreasing and sintering in a de-sintering integrated furnace, wherein Ar + 5% H is kept in the de-sintering integrated process2Keeping the temperature of 300 ℃ and 1000 ℃ for 1-2h respectively, then continuously and slowly heating to 1650 ℃ and keeping the temperature for 2h, slowly cooling to 900 ℃ and then cooling along with the furnace to obtain the sintered hollow UO2And (3) a core block.
Example 2
The preparation method of UO2 fuel pellet provided by this embodiment includes the following steps:
step 1, preparation of feedstock
Reducing the treated UO2Sieving the powder to obtain powder with the particle size of 10-200 mu m, wherein the binder adopts a polypropylene-paraffin-polystyrene-stearic acid system, the loading amount of the powder in the feed is 52 vol%, and the proportion of the binder is selected as follows: polypropylene PP (35%) + paraffin PW (40%) + polystyrene PS (20%) + stearic acid SA (5%). Preparing the feedstock in an internal mixer, maintaining the temperature at 170 ℃, adding polystyrene and polypropylene, then paraffin and stearic acid, and finally adding UO2Powder until the mixing is finished.
Step 2, injection molding process
Granulating the internally mixed feed, and adjusting the injection temperature (190-2The green body was injected.
Step 3, solvent degreasing
Mixing UO2And (3) carrying out solvent degreasing on the injection green body in dichloromethane, keeping the temperature of the solvent at 36 ℃, and removing partial paraffin.
Step 4, degreasing and sintering
Directly carrying out thermal degreasing and sintering in a de-sintering integrated furnace, wherein the de-sintering integration maintains Ar + 5% H2Keeping the temperature of 300 ℃ and 1000 ℃ for 1-2h respectively, then continuously and slowly heating to 1750 ℃ for sintering, keeping the temperature for 2h, slowly cooling to 900 ℃, and then cooling along with the furnace to obtain sintered hollow UO2And (3) a core block.

Claims (3)

1. A preparation method of UO2 fuel pellets is characterized by comprising the following steps: the method comprises the following steps:
step (1), preparation of feed; step (2), injection molding process; step (3), degreasing by using a solvent; step (4), degreasing and sintering;
the specific steps of the step (1) are as follows: reducing the treated UO2Sieving the powder, maintaining the temperature at 170 deg.C, adding polystyrene and polypropylene, then paraffin and stearic acid, and finallyPost-addition of UO2Powder is prepared until the mixing is finished;
the specific steps of the step (2) are as follows: after granulation in the step (1), obtaining hollow UO by injection on an injection molding machine2Injecting the green body;
the specific steps of the step (3) are as follows: mixing UO2Injecting the green body into flowing dichloromethane for solvent degreasing to remove partial paraffin;
the specific steps of the step (4) are as follows: after removing part of paraffin, directly carrying out thermal degreasing and sintering in a de-sintering integrated furnace, wherein Ar + 5% H is kept in the de-sintering integrated process2The temperature of the hollow UO is kept at 300 ℃ and 1000 ℃ for 1-2h respectively, then the temperature is slowly increased to 1650-1750 ℃ and kept at 2-4h, the temperature is slowly decreased to 900 ℃ and then the hollow UO is cooled along with the furnace to obtain the sintered hollow UO2A core block;
the UO2The particle size of the powder is 10-200 μm; the adhesive adopts a polypropylene-paraffin-polystyrene-stearic acid system, wherein the mass fraction of polypropylene in the adhesive is 30-40%, the mass fraction of paraffin is 35-45%, the mass fraction of polystyrene is 15-25%, and the mass fraction of stearic acid is 2-10%; the UO2 powder loading in the feed was: 48-55 vol%.
2. A method of making UO2 fuel pellets according to claim 1, characterized in that: the injection temperature is 190 ℃ and 220 ℃, and the injection pressure is 60-90 MPa.
3. A method of making UO2 fuel pellets according to claim 2, characterized in that: the temperature of the dichloromethane is 35-37 ℃.
CN201711471660.8A 2017-12-29 2017-12-29 Preparation method of UO2 fuel pellet Active CN109994235B (en)

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CN110415845B (en) * 2019-08-06 2021-06-11 中国核动力研究设计院 High-uranium-density composite fuel pellet and preparation method thereof

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CN1902271A (en) * 2003-11-14 2007-01-24 瓦尔德瑞沃咨询集团公司 Metal polymer composite, extrusion method thereof and product prepared thereby
CN101134242A (en) * 2007-10-17 2008-03-05 中南大学 Method of producing hard alloy rotatable special-shaped blade
CN105259291A (en) * 2015-11-11 2016-01-20 中国核动力研究设计院 Analysis method of fission gas
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US4064204A (en) * 1974-09-30 1977-12-20 General Atomic Company Manufacture of nuclear fuel compacts
DE3436705A1 (en) * 1984-10-06 1986-04-17 Gkss - Forschungszentrum Geesthacht Gmbh, 2054 Geesthacht Fuel plate for assembling light-water reactor cores, and process for the manufacture thereof
WO1995011509A1 (en) * 1993-10-22 1995-04-27 Japan Atomic Energy Research Institute Nuclear fuel cycle
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JP2005152984A (en) * 2003-11-27 2005-06-16 Nuclear Fuel Ind Ltd Injection molding device, and method of producing metal fuel molding
CN101134242A (en) * 2007-10-17 2008-03-05 中南大学 Method of producing hard alloy rotatable special-shaped blade
CN106663475A (en) * 2014-04-14 2017-05-10 先进核反应堆概念有限责任公司 Ceramic nuclear fuel dispersed in metallic alloy matrix
CN105259291A (en) * 2015-11-11 2016-01-20 中国核动力研究设计院 Analysis method of fission gas
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