JPS6236589A - Manufacture of nuclear-fuel sintered body containing gadolinium oxide - Google Patents
Manufacture of nuclear-fuel sintered body containing gadolinium oxideInfo
- Publication number
- JPS6236589A JPS6236589A JP60177194A JP17719485A JPS6236589A JP S6236589 A JPS6236589 A JP S6236589A JP 60177194 A JP60177194 A JP 60177194A JP 17719485 A JP17719485 A JP 17719485A JP S6236589 A JPS6236589 A JP S6236589A
- Authority
- JP
- Japan
- Prior art keywords
- sintered body
- oxide
- nuclear
- gadolinium oxide
- 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
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
- Compositions Of Oxide Ceramics (AREA)
Abstract
(57)【要約】本公報は電子出願前の出願データであるた
め要約のデータは記録されません。(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.
Description
【発明の詳細な説明】
〔発明の技術分野〕
本発明は、核燃料に関し、特に、燃焼特性ならびに機械
的特性にすぐれた酸化ガドリニウム入り核燃料焼結体の
製造方法に関する。DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to nuclear fuel, and particularly to a method for manufacturing a gadolinium oxide-containing nuclear fuel sintered body having excellent combustion characteristics and mechanical properties.
原子炉に使用されている核燃料は、二酸化ウラン、酸化
プルトニウム入り二酸化ウラン等の成分から構成され、
通常はこれら酸化物を成形、焼結して得られる焼結ベレ
ットとして用いられる。また、上記核燃料構成成分とし
ては、通常、中性子吸収物質として酸化ガドリニウム（
Ｇｄ２０３）が添加される。Nuclear fuel used in nuclear reactors is composed of components such as uranium dioxide and uranium dioxide containing plutonium oxide.
It is usually used as a sintered pellet obtained by molding and sintering these oxides. In addition, the above-mentioned nuclear fuel components usually include gadolinium oxide (
Gd203) is added.
ところで、一般に二酸化ウラン粉末に金属酸化物を混合
し、焼結すると、結晶粒径が変化することが知られてい
る。たとえば二酸化ウランに酸化ガドリニウムを混合し
、成形、焼結すると、４価のウランの一部分が６価のウ
ランに変化し、また焼結体は固溶体を作り複雑な様相を
示し、結晶粒径もＵＯ２のみを焼結した場合に比べ小さ
くなる。By the way, it is generally known that when a metal oxide is mixed with uranium dioxide powder and sintered, the crystal grain size changes. For example, when gadolinium oxide is mixed with uranium dioxide, molded, and sintered, a portion of the tetravalent uranium changes to hexavalent uranium, and the sintered body forms a solid solution, exhibiting a complex appearance, and the grain size of the UO2 It is smaller than when only sintered.
たとえば、ＵＯ２のみの焼結体の結晶粒径は１０〜２０
μｍ程度であるが、従来法で得られたＧｄ Ｏ入りＬ
Ｊ Ｏ２焼結体の結晶粒径は、通常２〜３μｍにまで小
さくなる。For example, the grain size of a sintered body containing only UO2 is 10 to 20
Although the size is about μm, the Gd O-containing L obtained by the conventional method
The crystal grain size of the JO2 sintered body is usually as small as 2 to 3 μm.
結晶粒が小さいと、結晶粒界までの空孔の平均自由行程
が短くなり、したがって粒界を通って消失するボアの量
が増加し、そのため照射時のデンシフィケーションが大
きくなるという問題が生ずる（たとえば、１７００℃、
２４時間試験で、Ｕ Ｏ２ベレツトの場合は１％ＴＤ内
外であるが、Ｇ ｄ ２０３入りＵ０２ベレットの場合
は２％ＴＯ近くまで増大する）。デンシフイケーション
の増大はベレットと被覆管のギャップが増大することを
意味し、これはベレットの中心温度の上昇へとつながる
。また、ベレット温度が上昇することは、ＦＰガスの放
出が活発になることを意味する。すなわち、焼結ベレッ
トの結晶粒が小さいとＦＰガスの放出が増大するという
問題が生ずる。さらに、従来の方法においては、ガドリ
ニウムの濃度が高くなるにつれて、焼結後にベレット表
面にクラックが発生しやすいという欠点がある。Smaller grains reduce the mean free path of the holes to the grain boundaries, thus increasing the amount of bores that disappear through the grain boundaries, leading to increased densification during irradiation. (For example, 1700℃,
In the 24-hour test, the TD for U O2 pellets is around 1% TD, but it increases to nearly 2% TO for U02 pellets containing G d 203). Increased densification means that the gap between the pellet and the cladding increases, which leads to an increase in the core temperature of the pellet. Furthermore, an increase in the pellet temperature means that the release of FP gas becomes more active. That is, if the crystal grains of the sintered pellet are small, a problem arises in that the release of FP gas increases. Furthermore, the conventional method has the disadvantage that as the concentration of gadolinium increases, cracks are more likely to occur on the pellet surface after sintering.
本発明は上述した点に鑑みてなされたものであり、原子
炉内での燃焼初期におけるデンシフイケーションの軽減
、ＦＰガス放出量の軽減が図られ、さらにクラック等の
欠陥が生じないような酸化ガドリニウム入り核燃料焼結
体の製造方法を提供すること、を目的とする。The present invention has been made in view of the above-mentioned points, and it is possible to reduce densification in the early stage of combustion in a nuclear reactor, reduce the amount of FP gas released, and further reduce oxidation so that defects such as cracks do not occur. The purpose of the present invention is to provide a method for manufacturing a gadolinium-containing nuclear fuel sintered body.
上記目的を達成するため、本発明の酸化ガドリニウム入
り核燃料焼結体の製造方法は、（イ）核燃料酸化物粉末
、（ロ）酸化ガドリニウム粉末、および（ハ）前記（イ
）と（ロ）の混合物の焼結温度よりも低い温度で溶融す
るか、または前記（イ）もしくは（ロ）と共晶反応を起
こす金属酸化物粉末、からなる原料粉末を成形し、焼結
することを特徴とする。In order to achieve the above object, the method for producing a gadolinium oxide-containing nuclear fuel sintered body of the present invention comprises (a) nuclear fuel oxide powder, (b) gadolinium oxide powder, and (c) the above (a) and (b). It is characterized by molding and sintering a raw material powder consisting of a metal oxide powder that melts at a temperature lower than the sintering temperature of the mixture or causes a eutectic reaction with the above (a) or (b). .
また、前記（ハ）の全８Ｍ化物は、酸素原子と金属原子
の化合比（０／Ｍ比）が２以上であることが、クラック
発生を防止する上で特に好ましい。Further, it is particularly preferable that the total 8M compound (c) has a combination ratio of oxygen atoms and metal atoms (0/M ratio) of 2 or more in order to prevent cracking.
以下、本発明をさらに詳細に説明する。以下の記載にお
いて、量を表わす「％」は、特に断らない限り重量基準
である。The present invention will be explained in more detail below. In the following description, "%" representing an amount is based on weight unless otherwise specified.
本発明で用いられる核燃料粉末としては、二酸化ウラン
その他の酸化ウラン、酸化プルトニウム、酸化トリウム
等の１種または２種以上に、さらに中性子吸収物質とし
て酸化ガドリニウムを加えた混合物が用いられる。The nuclear fuel powder used in the present invention is a mixture of one or more of uranium dioxide, other uranium oxides, plutonium oxide, thorium oxide, etc., and gadolinium oxide as a neutron absorbing substance.
粉末の粒径は、混合前において、約１０〜１５００μｍ
程度の範囲が好ましい。The particle size of the powder is approximately 10 to 1500 μm before mixing.
A range of degrees is preferred.
本発明では、焼結時における結晶粒成長を促進するため
に、特定の金属酸化物を添加する。この金属酸化物とし
ては、核燃料酸化物粉末と酸化物粉末との混合物の焼結
温度よりも低い温度で溶融するか、または共晶反応を起
こす金属酸化物が用いられ、特に、酸素原子と金属原子
の化合比（Ｏ／Ｍ）が２以上の化合物が好ましく用いら
れる。In the present invention, a specific metal oxide is added to promote crystal grain growth during sintering. As this metal oxide, a metal oxide that melts at a temperature lower than the sintering temperature of a mixture of nuclear fuel oxide powder and oxide powder or that causes a eutectic reaction is used. A compound having an atomic compound ratio (O/M) of 2 or more is preferably used.
このような金ａｍ化物としては、Ｎｂ２Ｏ５、Ｔ ｉ
ＯＭ ｏ Ｏａ、ＷＯ２等の遷移金ｆｉ酸化物２ゝ
が好ましく用いられ得るが、特に、Ｎｂ２Ｏ３、ＴｉＯ
２が好ましい。Such gold amides include Nb2O5, Ti
Transition gold fi oxides such as OM o Oa and WO2 can be preferably used, but in particular, Nb2O3, TiO
2 is preferred.
上記のような金属酸化物を添加することによって結晶粒
成長が促進される理由は必ずしも明らかではないが、次
の様に考えることができる。すなわち、ＵＯとＧ ｄ
２０３の混合物にさらに上記酸化物を添加すると、焼結
途中において、Ｕ Ｏ２とＧｄ２Ｏ３との固溶体の結晶
粒の周囲が溶融した上記金属酸化物で囲繞され、これに
よって結晶粒をいわば浮遊の状態にして結晶粒成長が促
進されるものと考えられる。このためには、上記金属酸
化物は、ＵＯとＧ ｄ ２０３との混合物の焼結温度（
通常１７００℃以上）よりも低い融点を有しているか、
または、該焼結温度よりも高温度の融点を有する金属酸
化物の場合は、ＵＯ２またはＧ ｄ ２０ ａと共晶反
応を起こし、その共晶温度は、上記焼結温度よりも低温
度でなければならない。The reason why crystal grain growth is promoted by adding metal oxides as described above is not necessarily clear, but it can be considered as follows. That is, UO and G d
When the above-mentioned oxide is further added to the mixture of No. 203, during sintering, the crystal grains of the solid solution of UO2 and Gd2O3 are surrounded by the above-mentioned molten metal oxide, thereby making the crystal grains in a so-called floating state. This is thought to promote grain growth. For this purpose, the metal oxide must be prepared at the sintering temperature of the mixture of UO and G d 203 (
(usually 1700℃ or higher), or
Alternatively, in the case of a metal oxide having a melting point higher than the sintering temperature, a eutectic reaction occurs with UO2 or G d 20 a, and the eutectic temperature must be lower than the sintering temperature. Must be.
このような条件を満足する金属酸化物としては、たとえ
ば、Ｎ ｂ ２０５ （融点１５００℃）、Ｔｉ０２（
共晶温度１５００℃）がある。Examples of metal oxides that satisfy these conditions include N b 205 (melting point 1500°C), Ti02 (
The eutectic temperature is 1500°C).
なお、添加づる金属酸化物の条件としては、上記融点、
共晶温度の他に、中性子吸収断面積も適宜考慮される。Note that the conditions for the metal oxide to be added include the above melting point,
In addition to the eutectic temperature, the neutron absorption cross section is also taken into consideration as appropriate.
さらに、上記金属酸化物は、酸素原子と金属原子の化合
比（０／Ｍ比）が２以上であることが、クラック発生を
防止する上で好ましい。０／Ｍ比が２．０以下では、Ｇ
ｄ２Ｏ３の濃度が高くなるにつれて焼結侵にペレット表
面にクラックが生じやすくなる。Furthermore, it is preferable that the metal oxide has a compounding ratio (0/M ratio) of oxygen atoms and metal atoms of 2 or more in order to prevent the occurrence of cracks. When the 0/M ratio is less than 2.0, G
As the concentration of d2O3 increases, cracks are more likely to occur on the pellet surface due to sintering corrosion.
Ｎｂ２０５（０／Ｍ＝２．５）を添加した場合、反応は
次の様に進み、これにより理論的には０／Ｍ＝２．０の
ベレン１−をつくることができ、クラックの発生を有効
に防止することができる。When Nb205 (0/M=2.5) is added, the reaction proceeds as follows, which theoretically makes it possible to create berene 1- with 0/M=2.0, which prevents the occurrence of cracks. It can be effectively prevented.
Ｇｄ１．５＋ＵＯ２＋Ｎｂ２０５−
（Ｇｄ、Ｎｂ、Ｕ）０２
０／Ｍ比を２．０以上にすることによってクラックの発
生が防止できる理由は必ずしも明らかではないが、次の
ように考えることができる。The reason why cracks can be prevented by setting the Gd1.5+UO2+Nb205- (Gd, Nb, U)020/M ratio to 2.0 or more is not necessarily clear, but it can be considered as follows.
Ｇｄ２Ｏ３がＵＯ３に固溶する場合は置換型固溶体を形
成する。Ｇｄ Ｏ固溶によるＵＯ２結晶体の欠陥方程式
は以下のように表現できる。When Gd2O3 forms a solid solution in UO3, a substitutional solid solution is formed. The defect equation of UO2 crystal due to GdO solid solution can be expressed as follows.
ここで
Ｇｄ’ ：Ｇｄ原子がＵ原子と置換した状態Ｏ′
：ＵＯ３の結晶体の酸素格子点にある酸素原子
Ｖ″ ：ＵＯ２結晶体の酸素格子点から酸素がぬけて
空孔になった状ｆ！
上記の欠陥方程式はＧｄ Ｏ分子がＵＯ２２分子と置
換固溶するたびに酸素空孔（Ｖ″）が１個形成されるこ
とを示している。Here, Gd': state O' in which Gd atom replaces U atom
:Oxygen atom V'' in the oxygen lattice point of UO3 crystal :Oxygen is removed from the oxygen lattice point of UO2 crystal and becomes a vacancyf! This shows that one oxygen vacancy (V'') is formed each time the material is melted.
この空孔は焼結時には還元雰囲気のため安定であるか、
焼結炉内から出て周囲の空気に触れると酸素を吸収しよ
うとして不安定となる。これがクラックの発生の一因と
考えることができる。Are these pores stable during sintering due to the reducing atmosphere?
When it comes out of the sintering furnace and comes into contact with the surrounding air, it tries to absorb oxygen and becomes unstable. This can be considered to be one of the reasons for the occurrence of cracks.
すなわち、Ｇ ｄ ２０ ａ濃度が高くなるほど、酸素
空孔（Ｖ”）１１度が高くなりクラックが発生しやすく
なると考えられる。That is, it is considered that as the G d 20 a concentration increases, the oxygen vacancy (V'') 11 degree increases and cracks are more likely to occur.
以下、本発明を実施例に基づいて説明するが、本発明は
これら実施例に限定されるものではない。The present invention will be described below based on Examples, but the present invention is not limited to these Examples.
まず、下表に示す組成の酸化ガドリニウム入り核燃料焼
結体原料を用意し、第１図に示す製造工程のフローチャ
ートに従って核燃料焼結体を作成した。First, a raw material for a nuclear fuel sintered body containing gadolinium oxide having the composition shown in the table below was prepared, and a nuclear fuel sintered body was created according to the flowchart of the manufacturing process shown in FIG.
Ｔｆ０２１５よびＮ ｂ ２０５のいずれも含有しない
組成物を比較例とした。A composition containing neither Tf0215 nor Nb205 was used as a comparative example.
表
上記組成の原料を、常法に従って機械混合し、予備成形
を行なって造粒した。その後、成形を行ない、該成形体
を耐熱ボートに入れ、所定の温度、時間で焼成した。焼
結雰囲気は水素である。The raw materials having the compositions shown in the table were mechanically mixed according to a conventional method, preformed, and granulated. Thereafter, molding was performed, and the molded body was placed in a heat-resistant boat and fired at a predetermined temperature and time. The sintering atmosphere is hydrogen.
上記表の結晶粒径の測定結果から明らかなように、本発
明の実施例に係るベレットは比較例に比べて、いずれも
結晶粒成長が見られた。また、結晶粒成長におよぼす効
果は、ＴｉＯ２の方がＮ ｂ ２０５よりも大きかった
。さらに、Ｎ ｂ ２０５の場合は、結晶粒成長効果の
他に、クラック発生防止効果が顕著に認められた。As is clear from the crystal grain size measurement results in the table above, crystal grain growth was observed in all of the pellets according to the examples of the present invention compared to the comparative examples. Furthermore, TiO2 had a greater effect on grain growth than Nb205. Furthermore, in the case of N b 205, in addition to the crystal grain growth effect, a remarkable crack prevention effect was observed.
第１図は、本発明の製造工程を示すフローチャートであ
る。FIG. 1 is a flowchart showing the manufacturing process of the present invention.
Claims (1)
粉末、および（ハ）前記（イ）と（ロ）の混合物の焼結
温度よりも低い温度で溶融するか、または前記（イ）も
しくは（ロ）と共晶反応を起こす金属酸化物粉末、から
なる原料粉末を成形し、焼結することを特徴とする、酸
化ガドリニウム入り核燃料焼結体の製造方法。 ２、前記（ハ）の金属酸化物が、酸素原子と金属原子の
化合比２以上の化合物である、特許請求の範囲第１項に
記載の方法。 ３、前記（ハ）の金属酸化物が、ＴｉＯ＿２またはＮｂ
＿２Ｏ＿５である、特許請求の範囲第１項または第２項
に記載の方法。[Claims] 1. (a) nuclear fuel oxide powder, (b) gadolinium oxide powder, and (c) melting at a temperature lower than the sintering temperature of the mixture of (a) and (b); Alternatively, a method for producing a gadolinium oxide-containing nuclear fuel sintered body, comprising molding and sintering a raw material powder made of a metal oxide powder that causes a eutectic reaction with the above (a) or (b). 2. The method according to claim 1, wherein the metal oxide (c) is a compound having a compounding ratio of oxygen atoms to metal atoms of 2 or more. 3. The metal oxide (c) is TiO_2 or Nb
_2O_5. The method according to claim 1 or 2, wherein the method is _2O_5.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP60177194A JPS6236589A (en) | 1985-08-12 | 1985-08-12 | Manufacture of nuclear-fuel sintered body containing gadolinium oxide |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP60177194A JPS6236589A (en) | 1985-08-12 | 1985-08-12 | Manufacture of nuclear-fuel sintered body containing gadolinium oxide |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS6236589A true JPS6236589A (en) | 1987-02-17 |
| JPH0371674B2 JPH0371674B2 (en) | 1991-11-14 |
Family
ID=16026820
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP60177194A Granted JPS6236589A (en) | 1985-08-12 | 1985-08-12 | Manufacture of nuclear-fuel sintered body containing gadolinium oxide |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS6236589A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS63117292A (en) * | 1986-11-04 | 1988-05-21 | 日本ニユクリア・フユエル株式会社 | Manufacture of nuclear fuel sintered body |
| JPH02236490A (en) * | 1989-03-10 | 1990-09-19 | Mitsubishi Nuclear Fuel Co Ltd | Production of nuclear fuel pellet containing gadolinium oxide having large crystal grain size |
| JPH0522295U (en) * | 1991-05-24 | 1993-03-23 | 鬼怒川パシフイツク株式会社 | Snorkel spoiler |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6097294A (en) * | 1983-10-06 | 1985-05-31 | シーメンス、アクチエンゲゼルシヤフト | Manufacture of oxide group nuclear fuel sintered body |
-
1985
- 1985-08-12 JP JP60177194A patent/JPS6236589A/en active Granted
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6097294A (en) * | 1983-10-06 | 1985-05-31 | シーメンス、アクチエンゲゼルシヤフト | Manufacture of oxide group nuclear fuel sintered body |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS63117292A (en) * | 1986-11-04 | 1988-05-21 | 日本ニユクリア・フユエル株式会社 | Manufacture of nuclear fuel sintered body |
| JPH02236490A (en) * | 1989-03-10 | 1990-09-19 | Mitsubishi Nuclear Fuel Co Ltd | Production of nuclear fuel pellet containing gadolinium oxide having large crystal grain size |
| JPH0522295U (en) * | 1991-05-24 | 1993-03-23 | 鬼怒川パシフイツク株式会社 | Snorkel spoiler |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0371674B2 (en) | 1991-11-14 |
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