CN101254950B - Method for surface oxidation treatment of uranium oxide powder - Google Patents

Method for surface oxidation treatment of uranium oxide powder Download PDF

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Publication number
CN101254950B
CN101254950B CN2008100695039A CN200810069503A CN101254950B CN 101254950 B CN101254950 B CN 101254950B CN 2008100695039 A CN2008100695039 A CN 2008100695039A CN 200810069503 A CN200810069503 A CN 200810069503A CN 101254950 B CN101254950 B CN 101254950B
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China
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powder
uranium dioxide
air
oxidation treatment
surface oxidation
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Expired - Fee Related
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CN2008100695039A
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CN101254950A (en
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高家诚
王勇
吴曙芳
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Chongqing University
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Chongqing University
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    • 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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Abstract

The invention relates to a method of oxidation treatment of a surface of a uranium dioxide, which is characterized that the method comprises the following steps: (1) taking the UO2 powder and puttingthe UO2 powder into a tube type atmosphere oven, heating the UO2 powder under the condition of oxidation medium while the heating rate is 5 to 20 degree centigrade per minute, heating the UO2 powder to 250 degree centigrade to 400 degree centigrade and insulating for 2 to 6 hours; (2) when the UO2 powder is cooled to 100 degree centigrade to the room temperature in the oven, taking the UO2 powderout and cooling the UO2 powder in the air, so as to obtain the uranium dioxide powder with the oxidized surface. The method puts the UO2 in different oxidation medium and the UO2 is insulated at a certain temperature, then the surface oxygen content is increased, the surface area is increased, and the O/U atomic ratio of uranium dioxide and the surface area of the UO2 powder are enhanced. The oxidation medium obtained by the method has rich resources, low oxidation temperature and less consumption and has the advantages of simple fabrication process and low cost.

Description

The method of powder of uranium dioxide surface oxidation treatment
Technical field
The present invention relates to a kind of surface oxidation treatment method, particularly a kind of to UO 2Carry out surface oxidation treatment, to improve the long-pending processing method of its O/U atomic ratio and specific surface area.
Background technology
Nuclear power is a kind of clean energy that has development potentiality, the UO that its reactor is used 2Fuel pellet is that sintering forms in about 1700 ℃ reducing atmosphere traditionally.Because the sintering temperature height, and need to use hydrogen atmosphere, so this technology has certain danger, and energy consumption is very high; Also must use high temperature sintering furnace and high temperature sintering with boat etc. simultaneously, cause its production cost higher.Along with worldwide problem of energy crisis shows especially and the enhancing of environmental consciousness day by day, the nuclear power demand of countries in the world continues to increase on the one hand, and the energy-saving and cost-reducing requirement of pellet sintering process also improves constantly on the other hand.
Therefore, low-temperature sintering (also the someone is referred to as double sintering or intermediate sintering temperature) technology is arisen at the historic moment.This technology is with UO 2Fuel pellet is sintering under the micro-oxidizing atmosphere about 1200 ℃ earlier, then final sintering in the reducing atmosphere about 1400 ℃.Because this energy consumption is low, with short production cycle, so obtain extensive concern in the recent period, especially is significant for China this energy-intensive developing country.Low-temperature sintering is activated sintering in essence.UO 2Sintering is the diffusion control process, because the spread coefficient of oxygen exceeds several magnitude than uranium, so the uranium diffusion is a controlling factor.Discover and departing from the UO of chemical dosage ratio 2In, the uranium diffusion activation energy is index decreased with the increase of excess oxygen.Therefore only guaranteed metachemistry dosage oxygen is at UO 2Existing in the pellet (being that the O/U atomic ratio is greater than 2), could realize low-temperature sintering effectively.Simultaneously, if will improve briquet density behind sintering velocity and the sintering, then need the powder of high-specific surface area, i.e. the metachemistry powder.
At present, the metachemistry powder is to use a certain proportion of UO 2Powder and U 3O 8Powder mixes forms, but studies show that, mixes UO 2U 3O 8Amount has certain limitation, otherwise can cause the briquet sinterability to descend greatly.Therefore this method has limited the increase rate of O/U atomic ratio.Sneak into U 3O 8Can not improve the specific surface area of powder.Simultaneously, directly add U 3O 8Particle also may cause the problem that reduction is not saturating, makes in the later pellet of final sintering still to have a small amount of U 3O 8, reduce the pellet performance.
Sintering process depends primarily on the surface property of powder, and surface oxidation treatment obtains excess of oxygen and mainly is present in particle surface, removes in reduction process easilier, and surface oxidation also can change granule-morphology, increasing specific surface area simultaneously.But at present to UO 2Carrying out the method for surface oxidation treatment does not appear in the newspapers as yet.
Summary of the invention
The method that the purpose of this invention is to provide a kind of powder of uranium dioxide surface oxidation treatment.The present invention is with UO 2Place different oxidizing mediums, insulation at a certain temperature increases its surface oxygen content increase, specific surface area, improves uranium dioxide O/U atomic ratio and powder of uranium dioxide specific surface area.Oxidizing medium of the present invention source is abundant, and oxidizing temperature is low, and less energy consumption has the advantage that manufacture craft is simple, cost is low.
In order to achieve the above object, employed raw material is 2.0 UO for the O/U atomic ratio 2Powder, Oxidant can be ventilating air, close stove air or water vapour, and oxidising process is carried out in tubular type atmosphere resistance furnace, and oxidizing temperature is 250-400 ℃, and temperature rise rate is 5-20 ℃/min, soaking time 2-6h.UO 2Powder furnace cooling to 100 takes out air cooling during ℃ to room temperature.
The invention has the beneficial effects as follows:
1) technology provided by the invention not only can improve the O/U atomic ratio of powder of uranium dioxide effectively, and can improve the surface-area (being specific surface area) of its unit weight, and the main thermodynamic driving force in the powder sintered just process of specific surface area, therefore, adopt this powder to carry out sintering, its thermodynamic driving force is higher than undressed powder, and sintering process is more prone to carry out.
2) oxidizing medium that uses of the present invention is air and water vapour, so the oxidizing medium source is abundant, and oxidizing temperature is low, less energy consumption, so cost of manufacture is cheap.
3) utilize the powder of uranium dioxide of the prepared O/U atomic ratio of the present invention greater than 2.0 (hyperstoichiometry ratios), that part of Sauerstoffatom (excess of oxygen) that wherein exceeds stoichiometric ratio mainly is present in powder particle surface, help promoting that uranium atom spreads at particle surface in the powder of uranium dioxide in the sintering process afterwards, improve the formation and the coarsening rate of particle connecting portion (being the sintering neck) in the sintering process, thereby reduce sintering temperature, quickening sintering velocity.
4) utilize the prepared hyperstoichiometry of the present invention to compare powder of uranium dioxide, its excessive oxygen mainly is present in powder particle surface, it is pressed into briquet when carrying out sintering, the excess of oxygen on surface reducing atmosphere easier and in the sintering oven in the reduction sintering process contacts, also be easy to get rid of, thereby ensure stoichiometry uranium dioxide (the O/U atomic ratio the is 2.0) content of firing in the knot finished product block by the intergranular residual porosities in the briquet.
With the powder of uranium dioxide that the method for the invention obtains, be used for follow-up sintering and be processed with to be beneficial to and promote uranium atom to spread at particle surface, improve the formation and the coarsening rate of sintering neck, reduce sintering temperature, accelerate sintering velocity.
Embodiment
With ventilating air, when closing stove air or water vapour and being oxidizing medium, follow these steps to handle powder of uranium dioxide:
1) gets UO 2Powder places Al 2O 3In the crucible, surface powder is wipeed off, it is sprawled in crucible evenly.
2) UO will be housed 2The crucible of powder is put into the tubular type atmosphere furnace, with ventilating air, close the stove air or water vapour is oxidizing medium, and heating, controlling its temperature rise rate is 5-20 ℃/min, is heated to 250 ℃～400 ℃, is incubated 2～6 hours;
3) with ventilating air or when closing the stove air and being oxidizing medium, directly connect the atmosphere furnace power supply under the condition of fire door and heat opening wide fire door or close respectively, insulation finishes the back power supply and cuts off automatically, treat that powder takes out air cooling below stove internal cooling to 100 ℃, promptly get the powder of uranium dioxide of surface of the present invention through oxide treatment;
When oxidizing medium is water vapour, close fire door earlier, powder of uranium dioxide is heated to 250 ℃～400 ℃, feed water vapour again, stop ventilation after insulation finishes, treat that furnace temperature drops to below 100 ℃, take out air cooling, promptly get the powder of uranium dioxide of surface of the present invention through oxide treatment.
Embodiment 1
Get original O/U atomic ratio and be 2.0, specific surface area is 2.70m 2The UO of/g 2Powder 20g, Al packs into 2O 3In the crucible, surface powder is wipeed off, and oxidizing medium is an air, and atmosphere is for opening wide fire door.UO will be housed 2The Al of powder 2O 3Crucible is put into tube furnace, and unlimited fire door is heated to 250 ℃, and temperature rise rate is about 10 ℃/min, and power supply cuts off automatically behind the insulation 2h, is cooled to about 90 ℃, takes out the crucible air cooling, promptly gets the powder of uranium dioxide of surface of the present invention through oxide treatment.
After tested, the UO after this art breading 2Powder O/U atomic ratio is 2.10, specific surface area is 2.90m 2/ g.
Embodiment 2
Get original O/U atomic ratio and be 2.0, specific surface area is 2.70m 2The UO of/g 2Powder 20g, Al packs into 2O 3In the crucible, surface powder is wipeed off, and oxidizing medium is an air, and atmosphere is for opening wide fire door.UO will be housed 2The Al of powder 2O 3Crucible is put into tube furnace, and unlimited fire door is heated to 300 ℃, and temperature rise rate is about 15 ℃/min, and power supply cuts off automatically behind the insulation 4h, is cooled to about 60 ℃, takes out the crucible air cooling, promptly gets the powder of uranium dioxide of surface of the present invention through oxide treatment.
After tested, the UO after this art breading 2Powder O/U atomic ratio is 2.35, specific surface area is 4.10m 2/ g.
Embodiment 3
Get original O/U atomic ratio and be 2.0, specific surface area is 2.70m 2The UO of/g 2Powder 20g, Al packs into 2O 3In the crucible, surface powder is wipeed off, and oxidizing medium is an air, and atmosphere is for closing the stove air.UO will be housed 2The Al of powder 2O 3Crucible is put into tube furnace, closes fire door and is heated to 300 ℃, and temperature rise rate is about 20 ℃/min, and power supply cuts off automatically behind the insulation 4h, is cooled to about 80 ℃, takes out the crucible air cooling, promptly gets the powder of uranium dioxide of surface of the present invention through oxide treatment.
After tested, the UO after this art breading 2Powder O/U atomic ratio is 2.29, specific surface area is 3.80m 2/ g.
Embodiment 4
Get original O/U atomic ratio and be 2.0, specific surface area is 2.70m 2The UO of/g 2Powder 20g, Al packs into 2O 3In the crucible, surface powder is wipeed off.Oxidizing medium is an air, and atmosphere is for closing the stove air.UO will be housed 2The Al of powder 2O 3Crucible is put into tube furnace, closes fire door and is heated to 360 ℃, and temperature rise rate is about 20 ℃/min, and power supply cuts off automatically behind the insulation 6h, is cooled to about 50 ℃, takes out the crucible air cooling, promptly gets the powder of uranium dioxide of surface of the present invention through oxide treatment.
After tested, the UO after this art breading 2Powder O/U atomic ratio is 2.43, specific surface area is 4.30m 2/ g.
Embodiment 5
Get original O/U atomic ratio and be 2.0, specific surface area is 2.70m 2The UO of/g 2Powder 20g, Al packs into 2O 3In the crucible, surface powder is wipeed off, and oxidizing medium is a water vapour, and atmosphere is water vapour.UO will be housed 2The Al of powder 2O 3Crucible is put into tube furnace, closes fire door and is heated to 300 ℃, and temperature rise rate is about 15 ℃/min, feed water vapour again, behind the insulation 4h, the power supply that stops to ventilate cuts off automatically, be cooled to about 70 ℃, take out the crucible air cooling, promptly get the powder of uranium dioxide of surface of the present invention through oxide treatment.
After tested, the UO after this art breading 2Powder O/U atomic ratio is 2.18, specific surface area is 3.50m 2/ g.
Embodiment 6
Get original O/U atomic ratio and be 2.0, specific surface area is 2.70m 2The UO of/g 2Powder 20g, Al packs into 2O 3In the crucible, surface powder is wipeed off, and oxidizing medium is a water vapour, and atmosphere is water vapour.UO will be housed 2The Al of powder 2O 3Crucible is put into tube furnace, closes fire door and is heated to 380 ℃, and temperature rise rate is about 15 ℃/min, feed water vapour again, behind the insulation 4h, the power supply that stops to ventilate cuts off automatically, be cooled to about 90 ℃, take out the crucible air cooling, promptly get the powder of uranium dioxide of surface of the present invention through oxide treatment.
After tested, the UO after this art breading 2Powder O/U atomic ratio is 2.43, specific surface area is 4.60m 2/ g.
Conclusion:
The foregoing description shows, adopts technology provided by the invention, at the blow-on air, to close under stove air and the water vapor conditions the O/U atomic ratio be 2.0 stoichiometry UO 2After powder carried out the thermal treatment of differing temps and time, its O/U atomic ratio was all brought up to more than 2.0, and specific surface area is also increased.

Claims (4)

1. the method for a powder of uranium dioxide surface oxidation treatment is characterized in that following steps are arranged:
1) will fill UO 2The container of powder is put into the tubular type atmosphere furnace, at oxidizing medium is to heat under the condition of air or water vapour, and temperature rise rate is 5-20 ℃/min, is heated to 250 ℃～400 ℃, is incubated 2～6 hours;
2) treat UO 2Powder during ℃ to room temperature, takes out air cooling at tubular type atmosphere furnace internal cooling to 100.
2. the method for powder of uranium dioxide surface oxidation treatment according to claim 1 is characterized in that: described air is ventilating air or closes the stove air.
3. the method for powder of uranium dioxide surface oxidation treatment according to claim 1, it is characterized in that: when oxidizing medium is air, open wide or close fire door, powder of uranium dioxide is heated to 250 ℃～400 ℃, be incubated 2～6 hours, during furnace cooling to 100 ℃～room temperature, take out powder of uranium dioxide, air cooling.
4. the method for powder of uranium dioxide surface oxidation treatment according to claim 1, it is characterized in that: when oxidizing medium is water vapour, close fire door earlier, powder of uranium dioxide is heated to 250 ℃～400 ℃, feeds water vapour again, be incubated 2～6 hours, after finishing, insulation stops ventilation, during furnace cooling to 100 ℃～room temperature, take out powder of uranium dioxide, air cooling.
CN2008100695039A 2008-03-26 2008-03-26 Method for surface oxidation treatment of uranium oxide powder Expired - Fee Related CN101254950B (en)

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Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101894594B (en) * 2009-09-11 2013-04-17 中国原子能科学研究院 Sub-stoichiometric UO2-xPreparation process of annular core block
CN107840372A (en) * 2016-09-20 2018-03-27 中核四〇四有限公司 A kind of MOX plutonium dioxide preprocessing method of raw materials

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
杨晓东等.二氧化铀芯块的低分压氧化性气氛烧结.原子能科学技术40 6.2006,40(6),682-687.
杨晓东等.二氧化铀芯块的低分压氧化性气氛烧结.原子能科学技术40 6.2006,40(6),682-687. *
许林水等.UO2粉末的热分析.中国核科技报告.1990,1-9. *

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