JP2000193775A - Producing method for nuclear fuel pellet - Google Patents
Producing method for nuclear fuel pelletInfo
- Publication number
- JP2000193775A JP2000193775A JP10377483A JP37748398A JP2000193775A JP 2000193775 A JP2000193775 A JP 2000193775A JP 10377483 A JP10377483 A JP 10377483A JP 37748398 A JP37748398 A JP 37748398A JP 2000193775 A JP2000193775 A JP 2000193775A
- Authority
- JP
- Japan
- Prior art keywords
- powder
- nuclear fuel
- pellets
- grinding
- sintering
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 239000008188 pellet Substances 0.000 title claims abstract description 85
- 239000003758 nuclear fuel Substances 0.000 title claims abstract description 31
- 238000000034 method Methods 0.000 title abstract description 27
- 239000000843 powder Substances 0.000 claims abstract description 80
- 239000002245 particle Substances 0.000 claims abstract description 72
- 238000005245 sintering Methods 0.000 claims abstract description 38
- OOAWCECZEHPMBX-UHFFFAOYSA-N oxygen(2-);uranium(4+) Chemical compound [O-2].[O-2].[U+4] OOAWCECZEHPMBX-UHFFFAOYSA-N 0.000 claims abstract description 36
- FCTBKIHDJGHPPO-UHFFFAOYSA-N uranium dioxide Inorganic materials O=[U]=O FCTBKIHDJGHPPO-UHFFFAOYSA-N 0.000 claims abstract description 36
- 238000000227 grinding Methods 0.000 claims abstract description 30
- CMIHHWBVHJVIGI-UHFFFAOYSA-N gadolinium(iii) oxide Chemical compound [O-2].[O-2].[O-2].[Gd+3].[Gd+3] CMIHHWBVHJVIGI-UHFFFAOYSA-N 0.000 claims abstract description 19
- 239000000654 additive Substances 0.000 claims abstract description 3
- 229910001938 gadolinium oxide Inorganic materials 0.000 claims abstract description 3
- 229940075613 gadolinium oxide Drugs 0.000 claims abstract description 3
- 239000002994 raw material Substances 0.000 claims description 32
- 238000004519 manufacturing process Methods 0.000 claims description 11
- 239000000203 mixture Substances 0.000 claims description 9
- FLDALJIYKQCYHH-UHFFFAOYSA-N plutonium(iv) oxide Chemical class [O-2].[O-2].[Pu+4] FLDALJIYKQCYHH-UHFFFAOYSA-N 0.000 claims description 5
- WZECUPJJEIXUKY-UHFFFAOYSA-N [O-2].[O-2].[O-2].[U+6] Chemical compound [O-2].[O-2].[O-2].[U+6] WZECUPJJEIXUKY-UHFFFAOYSA-N 0.000 claims description 3
- 239000006096 absorbing agent Substances 0.000 claims description 3
- 229910000439 uranium oxide Inorganic materials 0.000 claims description 3
- 230000000996 additive effect Effects 0.000 claims description 2
- 239000000463 material Substances 0.000 abstract description 14
- 238000000465 moulding Methods 0.000 abstract description 14
- 238000011084 recovery Methods 0.000 abstract description 7
- 150000002894 organic compounds Chemical class 0.000 abstract description 6
- 239000011812 mixed powder Substances 0.000 abstract description 4
- 238000012545 processing Methods 0.000 abstract description 4
- SHZGCJCMOBCMKK-KGJVWPDLSA-N beta-L-fucose Chemical compound C[C@@H]1O[C@H](O)[C@@H](O)[C@H](O)[C@@H]1O SHZGCJCMOBCMKK-KGJVWPDLSA-N 0.000 abstract 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 7
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 6
- 239000010931 gold Substances 0.000 description 6
- 229910052737 gold Inorganic materials 0.000 description 6
- 230000000694 effects Effects 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N nitrogen Substances N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
- 238000009826 distribution Methods 0.000 description 4
- 238000009837 dry grinding Methods 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- 239000001257 hydrogen Substances 0.000 description 4
- 229910052739 hydrogen Inorganic materials 0.000 description 4
- 238000002156 mixing Methods 0.000 description 4
- 229910052778 Plutonium Inorganic materials 0.000 description 3
- 238000005469 granulation Methods 0.000 description 3
- 230000003179 granulation Effects 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- OYEHPCDNVJXUIW-UHFFFAOYSA-N plutonium atom Chemical compound [Pu] OYEHPCDNVJXUIW-UHFFFAOYSA-N 0.000 description 3
- UTDLAEPMVCFGRJ-UHFFFAOYSA-N plutonium dihydrate Chemical compound O.O.[Pu] UTDLAEPMVCFGRJ-UHFFFAOYSA-N 0.000 description 3
- 239000011148 porous material Substances 0.000 description 3
- 238000003825 pressing Methods 0.000 description 3
- 238000010298 pulverizing process Methods 0.000 description 3
- 238000003303 reheating Methods 0.000 description 3
- 230000002159 abnormal effect Effects 0.000 description 2
- 229910052786 argon Inorganic materials 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- JCMLRUNDSXARRW-UHFFFAOYSA-N trioxouranium Chemical compound O=[U](=O)=O JCMLRUNDSXARRW-UHFFFAOYSA-N 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 238000001238 wet grinding Methods 0.000 description 2
- 238000007088 Archimedes method Methods 0.000 description 1
- 229910052770 Uranium Inorganic materials 0.000 description 1
- 238000001739 density measurement Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- -1 for example Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 230000001050 lubricating effect Effects 0.000 description 1
- 238000005461 lubrication Methods 0.000 description 1
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen(.) Chemical compound [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- JFALSRSLKYAFGM-UHFFFAOYSA-N uranium(0) Chemical compound [U] JFALSRSLKYAFGM-UHFFFAOYSA-N 0.000 description 1
- JFALSRSLKYAFGM-OIOBTWANSA-N uranium-235 Chemical compound [235U] JFALSRSLKYAFGM-OIOBTWANSA-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
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、原子炉燃料に使用
する核燃料ペレットの製造に関し、特に核燃料ペレット
の円筒面を研削加工する際に生成する研削粒子の再利用
に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the production of nuclear fuel pellets for use in nuclear reactor fuel, and more particularly to the reuse of abrasive particles produced when grinding cylindrical surfaces of nuclear fuel pellets.
【０００２】[0002]
【従来の技術】原子炉燃料として使用する核燃料ペレッ
トは、例えば二酸化ウランペレットの場合は、粉末を加
圧成形して円筒形の成形体とし、次いでこれを炉内を8
体積％程度以下の水蒸気を添加した、水素ガス、水素に
窒素を混合した混合ガス、あるいは水素ガスにアルゴン
を混合した混合ガス雰囲気とした焼結炉で、１６５０〜
１８００℃の温度で2〜6時間程度焼結した後、所定の直
径寸法の円筒体を得るために、円筒面を研削加工すると
いう方法で通常は製造される。また、中性子吸収材であ
るガドリニアを添加した二酸化ウランペレット(ガドリ
ニア添加二酸化ウランペレット)の場合や、二酸化ウラ
ンと二酸化プルトニウムとの混合酸化物ペレットの場合
も、二酸化ウラン粉末にガドリニア粉末を添加混合した
混合粉末を原料粉末とするか、あるいは二酸化ウラン粉
末と二酸化プルトニウム粉末を混合した混合粉末を原料
粉末とするかの違いはあるが、それらの原料粉末を加圧
成形して円筒形の成形体とし、これを炉内を8体積%程度
以下の水蒸気を添加した、水素ガス、水素に窒素を混合
した混合ガス、あるいは水素ガスにアルゴンを混合した
混合ガス雰囲気とした焼結炉で、１６５０〜１８００℃
の温度で2〜6時間焼結した後、所定の直径寸法の円筒面
を得るために、円筒面を研削加工するという方法で通常
は製造される。2. Description of the Related Art In the case of uranium dioxide pellets, for example, nuclear fuel pellets used as nuclear reactor fuel are obtained by press-molding powder into a cylindrical compact, which is then cooled in a reactor.
In a sintering furnace with a mixed gas atmosphere containing hydrogen gas, hydrogen mixed with nitrogen, or hydrogen gas mixed with argon to which a water vapor of not more than about% by volume is added,
After sintering at a temperature of 1800 ° C. for about 2 to 6 hours, it is usually manufactured by grinding a cylindrical surface to obtain a cylindrical body having a predetermined diameter. Also, in the case of uranium dioxide pellets added with gadolinia, which is a neutron absorber (gadolinia-added uranium dioxide pellets), and in the case of mixed oxide pellets of uranium dioxide and plutonium dioxide, gadolinia powder was added to uranium dioxide powder and mixed. There is a difference between using a mixed powder as a raw material powder or a mixed powder obtained by mixing a uranium dioxide powder and a plutonium dioxide powder as a raw material powder. In a sintering furnace in which the inside of the furnace is mixed with a hydrogen gas, a mixed gas of hydrogen and nitrogen, or a mixed gas of hydrogen and argon, to which about 8% by volume or less of steam has been added, 1650 to 1800 ° C
After sintering at a temperature of 2 to 6 hours, the cylindrical surface is usually ground to obtain a cylindrical surface having a predetermined diameter.
【０００３】ペレットに要求される特性の一つとして焼
結密度があり、これは二酸化ウランあるいはガドリニア
添加二酸化ウランあるいは二酸化ウランと二酸化プルト
ニウムの混合酸化物の理論上の密度を１００％とした場
合の相対密度として、例えば95.0〜97.0％相対密度(95.
0〜97.0％ＴＤと表記)という密度が要求される。この様
な密度のペレットを製造する方法としては、成形加圧時
の加圧力を調整することによって成形体の密度を調整し
たり、焼結時の焼結温度や焼結時間を調整する方法があ
る。この方法では、原料粉末の焼結特性によっては、ペ
レットに要求される他の特性である再焼結安定特性（焼
きしまり安定性）の要求を満足できないことがある。こ
の再焼結安定特性は、焼結したペレットを焼結時に近い
条件で数回にわたって再加熱した場合に、再加熱後の焼
結密度と焼結後、即ち再加熱前の焼結密度との差がある
一定以下の値となることが要求される。上記成形密度や
焼結条件を調整することによって焼結密度を調整する方
法では、焼結後のペレット中に再加熱によって消滅する
様な気孔が多く生成してしまうために、再加熱による密
度の上昇量が大きくなってしまう。One of the properties required for pellets is the sintered density, which is defined assuming that the theoretical density of uranium dioxide or gadolinia-added uranium dioxide or a mixed oxide of uranium dioxide and plutonium dioxide is 100%. As the relative density, for example, 95.0 to 97.0% relative density (95.
(Expressed as 0 to 97.0% TD). As a method of producing pellets having such a density, there is a method of adjusting the density of a molded body by adjusting the pressing force at the time of molding pressure, or adjusting the sintering temperature or sintering time at the time of sintering. is there. In this method, depending on the sintering characteristics of the raw material powder, the resintering stability characteristics (baking stability), which is another characteristic required for the pellets, may not be satisfied. This resintering stability characteristic is that when the sintered pellet is reheated several times under conditions close to the time of sintering, the sintered density after reheating and after sintering, that is, the sintered density before reheating, It is required that the difference be a certain value or less. In the method of adjusting the sintering density by adjusting the molding density and the sintering conditions, many pores that disappear by reheating are generated in the pellet after sintering. The amount of rise will be large.
【０００４】そこで、成形密度や焼結条件を調整するこ
とによって焼結密度を調整する前記方法では、要求され
る焼結密度と再焼結安定特性を同時には満足できない場
合には、焼結時に熱分解蒸発してしまう有機化合物の粉
末や、例えば焼結した二酸化ウランペレットを空気中で
加熱酸化することによって得られる八三酸化ウラン（Ｕ
3 Ｏ8 ）の微細な粉末を、気孔形成材として原料粉末に
添加して、加圧成形、焼結することによって焼結ペレッ
トを製造する方法が通常行われている。また、ペレット
の取扱い時の衝撃等によって割れ欠けを生じたペレット
は、湿式回収処理により再利用可能な原料粉末に加工さ
れたり、上述の様に、空気中での加熱酸化処理によりＵ
3 Ｏ8 の微細な粉末として原料粉末に添加することによ
って再利用されているが、焼結ペレットを研削する際に
生成する核燃料焼結体の研削粒子は、空気中でそのまま
加熱酸化しても微細な粉末とはならないため、湿式回収
処理により再利用可能な原料粉末に加工されて再利用さ
れている。Therefore, in the above method of adjusting the sintering density by adjusting the molding density and the sintering conditions, if the required sintering density and resintering stability characteristics cannot be satisfied simultaneously, the Powders of organic compounds which are thermally decomposed and evaporated, and uranium trioxide (U) obtained by heating and oxidizing sintered uranium dioxide pellets in air, for example.
A method of manufacturing a sintered pellet by adding a fine powder of 3 O 8 ) to a raw material powder as a pore-forming material, and then performing pressure molding and sintering is usually performed. In addition, pellets that have been cracked due to impact during handling of the pellets are processed into reusable raw material powders by wet recovery processing, or as described above, are heated and oxidized in air to produce U.S. powder.
Although it is reused by adding it to the raw material powder as a fine powder of 3 O 8 , the ground particles of the nuclear fuel sintered body generated when grinding the sintered pellets can be heated and oxidized as they are in the air. Since it does not become fine powder, it is processed into a reusable raw material powder by wet recovery processing and reused.
【０００５】しかし、上記従来の製造方法では、有機化
合物の気孔形成材を使用すると、その材料コストがかか
ることになり、また研削粒子を再利用するためには、湿
式回収処理コストを要することになる。[0005] However, in the above-mentioned conventional manufacturing method, when a pore-forming material of an organic compound is used, the material cost is increased, and in order to reuse the abrasive particles, a wet recovery processing cost is required. Become.
【０００６】[0006]
【発明が解決しようとする課題】本発明の目的は、核燃
料ペレットを製造する場合、焼結密度調整のために使用
する、有機化合物の気孔形成材のための材料コストや、
核燃料焼結体の研削粒子を再利用する際に必要となる湿
式回収処理コストを低減することにある。SUMMARY OF THE INVENTION It is an object of the present invention to provide a nuclear fuel pellet in which the material cost for an organic compound pore-forming material used for adjusting the sintering density,
An object of the present invention is to reduce the cost of a wet recovery process required when reusing the ground particles of a nuclear fuel sintered body.
【０００７】[0007]
【課題を解決するための手段】（１） 原料として核燃
料の粉末を使用し、この粉末を加圧成形、焼結、研削し
て核燃料ペレットとする製造方法において、ペレットの
焼結密度を調整するために原料粉末に添加する添加物と
して、90μm以下の粒径を有する、焼結ペレットを研削
する際に生成する核燃料焼結体の研削粒子を使用し、こ
の研削粒子を原料粉末に添加してから、加圧成形、焼
結、研削することを特徴とする核燃料ペレットの製造方
法。 （２） 核燃料が、二酸化ウラン、その他の酸化ウラ
ン、二酸化プルトニウムの１種または２種以上の混合
物、或いはそれら１種または２種以上の混合物と、中性
子吸収材である酸化ガドリニウム（ガドリニア）との混
合物である前記（１）に記載の核燃料ペレットの製造方
法。Means for Solving the Problems (1) In a production method in which nuclear fuel powder is used as a raw material, and this powder is pressed, sintered, and ground into a nuclear fuel pellet, the sintered density of the pellet is adjusted. As an additive to be added to the raw material powder, having a particle size of 90 μm or less, use the ground particles of the nuclear fuel sintered body generated when grinding the sintered pellets, and add the ground particles to the raw material powder , Sintering, and grinding. (2) The nuclear fuel is uranium dioxide, another uranium oxide, one or more of a mixture of plutonium dioxides, or a mixture of one or more of them, and gadolinium oxide (gadolinia) as a neutron absorber. The method for producing nuclear fuel pellets according to the above (1), which is a mixture.
【０００８】本発明の方法は、焼結ペレットを研削する
際に生成する核燃料焼結体の研削粒子の中から、適切な
粒径を有する研削粒子を選別し、得られた研削粒子を気
孔形成材として原料粉末に添加し、添加後は従来と同様
な加圧成形、焼結、研削を行うことによって核燃料ペレ
ットを製造する方法である。According to the method of the present invention, grinding particles having an appropriate particle size are selected from among the grinding particles of a nuclear fuel sintered body generated when grinding a sintered pellet, and the obtained grinding particles are formed into pores. This is a method in which nuclear fuel pellets are produced by adding a material to a raw material powder and then performing pressure molding, sintering and grinding in the same manner as before.
【０００９】本発明者らは、核燃料焼結体の研削粒子を
原料粉末に添加して、加圧成形、焼結を行って得られた
ペレットの焼結密度が、研削粒子を添加しない原料粉末
を、同条件で加圧成形、焼結を行って得られたペレット
の焼結密度よりも低下する、即ち、研削粒子が気孔形成
材としての効果を有していることを実験的に見い出し
た。しかし、ただ単に、焼結ペレットを研削する際に生
成する研削粒子を添加しただけでは、焼結密度は低下さ
せることができるものの、ペレットの金相的微細組織に
おいて異常なボイドや結晶粒を生じるとともに、ペレッ
ト表面性状において許容できない程度の突起を生じてし
まうことも同時に観察された。そこで、研削粒子を分級
して、種々の粒径分布を有する研削粒子に対して、同様
な試験を行った結果、適切な粒径分布を有する研削粒子
を使用することにより、金相的微細組織における異常な
ボイドや結晶粒、並びにペレット表面性状における許容
できない突起を生じさせないでペレットを製造できる条
件を見い出した。[0009] The inventors of the present invention added the ground particles of the nuclear fuel sintered body to the raw material powder, and performed pressure molding and sintering. Under pressure molding and sintering under the same conditions, lower than the sintering density of the pellets obtained, that is, it was experimentally found that the ground particles have an effect as a pore-forming material. . However, simply adding grinding particles generated when grinding sintered pellets can reduce the sintering density, but causes abnormal voids and crystal grains in the gold phase microstructure of the pellets At the same time, it was also observed that unacceptable protrusions were produced in the pellet surface properties. Therefore, the grinding particles were classified, and a similar test was performed on the grinding particles having various particle size distributions. As a result, by using the grinding particles having an appropriate particle size distribution, the metal phase microstructure was obtained. The conditions under which pellets can be produced without causing abnormal voids and crystal grains and unacceptable protrusions in the surface properties of the pellets have been found.
【００１０】本発明方法では、焼結ペレットを研削する
際に生成する核燃料焼結体の研削粒子を、９０μｍ以下
の粒径を有する様に分級し、この分級された研削粒子
を、原料となる核燃料粉末に添加し、添加された粉末を
加圧成形、焼結、研削してペレットとすることによっ
て、正常な金相的微細組織並びに外観性状を有し、かつ
所定の焼結密度を有するペレットを製造することができ
る。In the method of the present invention, the ground particles of the nuclear fuel sintered body generated when grinding the sintered pellets are classified so as to have a particle size of 90 μm or less, and the classified ground particles are used as a raw material. Pellets having a normal metallographic microstructure and appearance properties, and having a predetermined sintered density by being added to nuclear fuel powder, and pressing the added powder, sintering, and grinding into pellets. Can be manufactured.
【００１１】図1、図2及び図3は、本発明の方法の一例
を含む、核燃料ペレットの製造方法の一連の工程を示す
説明図である。FIGS. 1, 2 and 3 are explanatory views showing a series of steps of a method for producing nuclear fuel pellets, including an example of the method of the present invention.
【００１２】研削粒子の気孔形成材としての焼結密度低
下効果は、研削粒子の原料粉末に対する重量割合とし
て、研削粒子添加率１％に対して約0.2 ％ＴＤ程度であ
るため、研削粒子添加率については、原料粉末の焼結特
性と、目標とするペレットの焼結密度との関係に依存す
ることになる。例えば、原料粉末を単独で使用してペレ
ットを製造した場合に、ペレットの焼結密度が97.5％Ｔ
Ｄとなる様な原料粉末を使用して、96.5%TDの焼結密度
を有するペレットを製造しようとする場合には、重量比
率で約5％の研削粒子を添加することになる。また、研
削粒子は有機化合物の粉末やＵ3０8といった気孔形成材
との併用も可能であるため、上述の原料粉末に0.4％Ｔ
Ｄの焼結密度低下を生じさせる気孔形成材を添加して9
6.5％ＴＤの焼結密度を有するペレットを製造しようと
する場合には、重量比率で約3％の研削粒子を添加する
ことになる。また、添加する研削粒子の濃縮度（酸化ウ
ランの場合は全ウランに対するウラン235伺位体の比
率）やガドリニア添加率やプルトニウム富化度は、添加
される原料粉末の濃縮度やガドリニア添加率やプルトニ
ウム富化度と同じものが通常は添加されるが、異なった
濃縮度やガドリニア添加率やプルトニウム富化度の研削
粒子を添加しても本発明による効果は何等失われること
はない。また、焼結ペレットの研削方法には、水等の冷
却/潤滑材をかけながら研削する湿式研削法と、その様
な冷却/潤滑材を使用しない乾式研削法があるが、乾式
研削法で生成した研削粒子の場合はそのまま分級できる
のに対して、湿式研削法で生成した研削粒子の場合は、
乾燥、粉砕後分級した方が良いという相違があるだけ
で、いずれの研削法で生成した研削粒子も、90μm以下
に分級されたものであれば、本発明による効果に影響を
及ぼさない。更に、90μm以下に分級した研削粒子を原
料粉末に添加する際には、両者を十分に混合する必要は
あるが、混合した粉末は図1に示す工程のようにそのま
ま加圧成形に供しても良いし、図2もしくは図3に示す工
程のように粉砕、造粒等の処理を行ってから加圧成形に
供してもかまわない。The effect of reducing the sintering density of the abrasive particles as a pore-forming material is about 0.2% TD in terms of the weight ratio of the abrasive particles to the raw material powder, which is about 0.2% TD per 1% of the abrasive particles. Depends on the relationship between the sintering characteristics of the raw material powder and the target sintering density of the pellets. For example, when pellets are manufactured using the raw material powder alone, the sintered density of the pellets is 97.5% T
When pellets having a sintering density of 96.5% TD are to be produced by using a raw material powder such as D, about 5% by weight of ground particles will be added. Further, since the grinding particles can be combined with pore forming materials such as powder or U 3 0 8 organic compound, 0.4% to the raw material powder above T
D by adding a pore-forming material that causes a decrease in the sintered density of D
If pellets having a sintering density of 6.5% TD are to be produced, about 3% by weight of ground particles will be added. The enrichment of the added abrasive particles (the ratio of the uranium 235 interrogator to the total uranium in the case of uranium oxide), the gadolinia addition rate, and the plutonium enrichment are determined by the enrichment and gadolinia addition rates of the added raw material powder. The same plutonium enrichment is usually added, but the addition of ground particles with different enrichment, gadolinia addition or plutonium enrichment does not lose any of the effects of the present invention. There are two methods for grinding sintered pellets: wet grinding, which involves grinding while cooling / lubricating with water, and dry grinding, which does not use such cooling / lubrication. In the case of ground particles that have been subjected to wet grinding,
The only difference is that it is better to classify after drying and pulverization. The effect of the present invention is not affected as long as the ground particles generated by any of the grinding methods are classified to 90 μm or less. Furthermore, when adding the ground particles classified to 90 μm or less to the raw material powder, it is necessary to sufficiently mix both, but the mixed powder may be subjected to pressure molding as it is in the process shown in FIG. Alternatively, it may be subjected to a process such as pulverization and granulation as in the process shown in FIG. 2 or FIG.
【００１３】[0013]
【実施例】以下に、本発明を実施例と比較例によりさら
に説明する。原料粉末として二酸化ウラン粉末を使用
し、これに二酸化ウラン焼結ペレットの円筒面を研削機
で研削して得られた研削粒子を添加して加圧成形、焼
結、研削を行って各種ペレットを製造した。二酸化ウラ
ン焼結ペレットを乾式研削して得られた研削粒子の分級
前の粒径分布は、図４に示す通りである。The present invention will be further described below with reference to examples and comparative examples. Uranium dioxide powder is used as a raw material powder, and grinding particles obtained by grinding the cylindrical surface of a uranium dioxide sintered pellet with a grinder are added thereto, followed by pressing, sintering, and grinding to form various pellets. Manufactured. The particle size distribution of the ground particles obtained by dry-grinding the uranium dioxide sintered pellets before classification is as shown in FIG.
【００１４】供試材として用いたペレットは次の４種類
であり、研削粒子の添加以外は同一のペレット製造条件
である。すなわち、比較用試料として二酸化ウラン粉末
のみのペレット（試料番号１）、二酸化ウラン粉末に分
級しない研削粒子を重量比で３％添加した粉末を使用し
たペレット（試料番号２）、二酸化ウラン粉末に目開き
１２５μｍの篩を通過した、乾式研削法により生成した
研削粒子を重量比で３％添加した粉末を使用したペレッ
ト（試料番号３）および二酸化ウラン粉末に目開き９０
μｍの篩を通過した、乾式研削法により生成した研削粒
子を重量比で３％添加した粉末を使用したペレット（試
料番号４）である。The following four types of pellets were used as test materials, and the pellet production conditions were the same except for the addition of abrasive particles. Specifically, as comparative samples, pellets containing only uranium dioxide powder (sample No. 1), pellets using powder containing 3% by weight of ground particles not classified as uranium dioxide powder (sample number 2), and uranium dioxide powder were used. Pellet (sample No. 3) using powder containing 3% by weight of ground particles produced by dry grinding and passing through a 125 μm opening sieve, and a uranium dioxide powder with an opening of 90%
This is a pellet (sample No. 4) using a powder that has passed through a sieve of μm and added with 3% by weight of ground particles produced by a dry grinding method at a weight ratio.
【００１５】上記４種類のペレットの製造条件について
説明する。まず、二酸化ウラン粉末に重量比率で３％
（二酸化ウラン粉末のみの場合は０％）となる様に計量
した研削粒子を加え、Ｖ型混合機で充分に二酸化ウラン
粉末と研削粒子を混合した。次に、一軸加圧式油圧プレ
スを用いて、成形圧力２．３ｔ／ｃｍ2 の圧力で加圧成
形して円筒形成形体とした後、焼結炉を用いて、水素７
５％＋窒素２５％の混合ガス（水蒸気添加率１％）雰囲
気で、６００℃／時間の昇温速度で１７５０℃迄昇温
し、３時間保持後室温迄降温して焼結ペレットを得た
後、この焼結ペレットの円筒面を研削機で研削してペレ
ットを得た。The production conditions for the above four types of pellets will be described. First, 3% by weight of uranium dioxide powder
(In the case of only uranium dioxide powder, 0% was added), and the uranium dioxide powder and the ground particles were sufficiently mixed with a V-type mixer. Next, using a uniaxial pressurizing hydraulic press, press-forming at a pressure of 2.3 t / cm 2 to form a cylindrical body, and then using a sintering furnace, hydrogen
In a mixed gas atmosphere of 5% + nitrogen 25% (steam addition rate: 1%), the temperature was raised to 1750 ° C. at a rate of 600 ° C./hour, and after holding for 3 hours, the temperature was lowered to room temperature to obtain sintered pellets. Thereafter, the cylindrical surface of the sintered pellet was ground by a grinder to obtain a pellet.
【００１６】得られた４種のペレットにつき、アルキメ
デス法で密度を測定し、また外観を観察した後、金相試
験を行って評価した。The densities of the obtained four types of pellets were measured by the Archimedes method, and the appearance was observed.
【００１７】表１に各ペレットの密度測定結果と評価結
果を示す。また、図５と図９は、試料番号１のペレット
の、図６と図１０は試料番号２のペレットの、図７と図
１１は試料番号３のペレットの、および図８と図１２は
試料番号４のペレットのそれぞれ外観写真と金相写真で
ある。Table 1 shows the density measurement results and evaluation results of each pellet. FIGS. 5 and 9 show the pellets of sample No. 1, FIGS. 6 and 10 show the pellets of sample No. 2, FIGS. 7 and 11 show the pellets of sample No. 3, and FIGS. It is an external appearance photograph and a metal phase photograph of the pellet of number 4, respectively.
【００１８】[0018]
【表１】 [Table 1]
【００１９】図５〜８の外観写真から、分級しない研削
粒子を添加した場合にはペレット表面に研削粒子の作用
による許容できない突起が現れ、また目開き１２５μｍ
の篩を通過した研削粒子を添加した場合にはペレット表
面に研削粒子の作用による若干の突起が見られるのに対
して、目開き９０μｍの篩を通過した研削粒子を添加し
た場合には、比較用として二酸化ウラン粉末のみから製
造した場合と同等の外観をもつペレットが得られること
が分る。From the appearance photographs of FIGS. 5 to 8, when unclassified abrasive particles are added, unacceptable protrusions appear on the pellet surface due to the action of the abrasive particles, and the openings are 125 μm.
When the abrasive particles passed through a sieve were added, some protrusions due to the effect of the abrasive particles were seen on the pellet surface, whereas when the abrasive particles passed through a sieve with an opening of 90 μm were added, the comparison was made. It can be seen that pellets having the same appearance as those produced from uranium dioxide powder alone are obtained.
【００２０】また、図９〜１２の金相写真から、分級し
ない研削粒子を添加した場合には金相的微細組織に研削
粒子の作用によるボイドが現れるのに対して、目開き１
２５μｍの篩を通過した研削粒子を添加した場合、及び
目開き９０μｍの篩を通過した研削粒子を添加した場合
には、二酸化ウラン粉末のみから製造した場合と同等の
金相的微細組織をもつペレットが得られることが分る。Also, from the gold phase photographs shown in FIGS. 9 to 12, when the non-classified ground particles are added, voids due to the action of the ground particles appear in the fine metal-like microstructure.
When the abrasive particles passed through a 25 μm sieve were added, and when the abrasive particles passed through a 90 μm sieve were added, pellets having a metal phase microstructure equivalent to that produced from only uranium dioxide powder were obtained. Is obtained.
【００２１】[0021]
【発明の効果】本発明方法によれば、適切な粒径を有す
る様に選別した研削粒子を、原料となる核燃料粉末に、
原料粉末の焼結性と目標とするペレットの焼結密度との
関係から決定される添加率で添加してペレットを製造す
ることにより、従来と同等のペレットが製造できること
になり、従来気孔形成材として使用している有機化合物
の材料コストを低減できるとともに、湿式回収処理を行
って再利用しなければらならい研削粒子を粒径の大きな
ものだけにすることによって、湿式回収コストを低減で
きることになる。According to the method of the present invention, ground particles selected to have an appropriate particle size are converted into nuclear fuel powder as a raw material,
By adding pellets at an addition rate determined from the relationship between the sinterability of the raw material powder and the target sintering density of the pellets, pellets equivalent to conventional ones can be manufactured, and the conventional pore-forming material In addition to reducing the material cost of the organic compound used as a raw material, the wet recovery cost can be reduced by using only the abrasive particles having a large particle diameter that must be reused by performing the wet recovery process.
【図１】本発明の方法のうち、原料粉末と研削粒子を混
合後そのまま加圧成形に供する方法の概略を示す工程図
である。FIG. 1 is a process diagram showing an outline of a method of mixing a raw material powder and ground particles and subjecting it to pressure molding as it is in the method of the present invention.
【図２】本発明の方法のうち、原料粉末と研削粒子を混
合後、造粒処理を行ってから加圧成形に供する方法の概
略を示す工程図である。FIG. 2 is a process chart showing an outline of a method of mixing a raw material powder and ground particles, performing a granulation treatment and then subjecting the mixture to pressure molding in the method of the present invention.
【図３】本発明の方法のうち、原料粉末と研削粒子を混
合後、粉砕し造粒処理を行ってから加圧成形に供する方
法の概略を示す工程図である。FIG. 3 is a process diagram showing an outline of a method of mixing a raw material powder and ground particles, pulverizing the raw material powder and performing a granulation treatment, and then subjecting the raw material powder to pressure molding in the method of the present invention.
【図４】二酸化ウランペレットの研削粒子の分級前の粒
径分布を示すグラフである。FIG. 4 is a graph showing a particle size distribution of ground particles of uranium dioxide pellets before classification.
【図５】二酸化ウラン粉末のみを使用したペレットの外
観写真である。FIG. 5 is an external photograph of a pellet using only uranium dioxide powder.
【図６】二酸化ウラン粉末に分級しない研削粒子を重量
比率で３％添加した粉末を使用したペレットの外観写真
である。FIG. 6 is an external photograph of a pellet using a powder obtained by adding 3% by weight of ground particles that are not classified to uranium dioxide powder.
【図７】二酸化ウラン粉末に目開き１２５μｍの篩を通
過した研削粒子を重量比率で３％添加した粉末を使用し
たペレットの外観写真である。FIG. 7 is an external photograph of a pellet using a powder obtained by adding 3% by weight of ground particles that have passed through a 125 μm mesh sieve to uranium dioxide powder.
【図８】二酸化ウラン粉末に目開き９０μｍの篩を通過
した研削粒子を重量比率で３％添加した粉末を使用した
ペレットの外観写真である。FIG. 8 is an external photograph of a pellet using a powder obtained by adding 3% by weight of ground particles that have passed through a sieve having a mesh size of 90 μm to uranium dioxide powder.
【図９】二酸化ウラン粉末のみを使用したペレットの金
相写真である。FIG. 9 is a photograph of a gold phase of a pellet using only uranium dioxide powder.
【図１０】二酸化ウラン粉末に分級しない研削粒子を重
量比率で３％添加した粉末を使用したペレットの金相写
真である。FIG. 10 is a photograph of a gold phase of a pellet using a powder obtained by adding 3% by weight of ground particles that are not classified to uranium dioxide powder.
【図１１】二酸化ウラン粉末に目開き１２５μｍの篩を
通過した研削粒子を重量比率で３％添加した粉末を使用
したペレットの金相写真である。FIG. 11 is a photograph of a gold phase of a pellet using a powder obtained by adding 3% by weight of ground particles, which have passed through a sieve having an aperture of 125 μm, to uranium dioxide powder.
【図１２】二酸化ウラン粉末に目開き９０μｍの篩を通
過した研削粒子を重量比率で３％添加した粉末を使用し
たペレットの金相写真である。FIG. 12 is a photograph of a gold phase of a pellet using a powder obtained by adding 3% by weight of ground particles that have passed through a sieve having an opening of 90 μm to uranium dioxide powder.
Claims (2)
末を加圧成形、焼結、研削して核燃料ペレットとする製
造方法において、ペレットの焼結密度を調整するために
原料粉末に添加する添加物として、90μm以下の粒径を
有する、焼結ペレットを研削する際に生成する核燃料焼
結体の研削粒子を使用し、この研削粒子を原料粉末に添
加してから、加圧成形、焼結、研削することを特徴とす
る核燃料ペレットの製造方法。1. A method for producing nuclear fuel pellets by using a nuclear fuel powder as a raw material and press-forming, sintering and grinding the powder to add the raw material powder in order to adjust the sintered density of the pellet. As an additive, use is made of ground particles of a nuclear fuel sintered body generated when grinding sintered pellets having a particle size of 90 μm or less, and the ground particles are added to the raw material powder, and then pressed and sintered. A method for producing nuclear fuel pellets, comprising sintering and grinding.
ラン、二酸化プルトニウムの１種または２種以上の混合
物、或いはそれら１種または２種以上の混合物と、中性
子吸収材である酸化ガドリニウム（ガドリニア）との混
合物である請求項１に記載の核燃料ペレットの製造方
法。2. The nuclear fuel is uranium dioxide, another uranium oxide, one or more of a mixture of plutonium dioxides, or a mixture of one or more of these, and gadolinium oxide (gadolinia) as a neutron absorber. The method for producing nuclear fuel pellets according to claim 1, wherein the mixture is a mixture with:
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP37748398A JP3403960B2 (en) | 1998-12-28 | 1998-12-28 | Method for producing nuclear fuel pellets |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP37748398A JP3403960B2 (en) | 1998-12-28 | 1998-12-28 | Method for producing nuclear fuel pellets |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2000193775A true JP2000193775A (en) | 2000-07-14 |
| JP3403960B2 JP3403960B2 (en) | 2003-05-06 |
Family
ID=18508886
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP37748398A Expired - Fee Related JP3403960B2 (en) | 1998-12-28 | 1998-12-28 | Method for producing nuclear fuel pellets |
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| Country | Link |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100446587B1 (en) * | 2001-09-19 | 2004-09-04 | 한국수력원자력 주식회사 | Method of manufacturing uranium dioxide pellets with high creep rate |
-
1998
- 1998-12-28 JP JP37748398A patent/JP3403960B2/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100446587B1 (en) * | 2001-09-19 | 2004-09-04 | 한국수력원자력 주식회사 | Method of manufacturing uranium dioxide pellets with high creep rate |
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| Publication number | Publication date |
|---|---|
| JP3403960B2 (en) | 2003-05-06 |
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