JP2672420B2 - Mixed oxide fuel pellet and method for producing the same - Google Patents
Mixed oxide fuel pellet and method for producing the sameInfo
- Publication number
- JP2672420B2 JP2672420B2 JP3241253A JP24125391A JP2672420B2 JP 2672420 B2 JP2672420 B2 JP 2672420B2 JP 3241253 A JP3241253 A JP 3241253A JP 24125391 A JP24125391 A JP 24125391A JP 2672420 B2 JP2672420 B2 JP 2672420B2
- Authority
- JP
- Japan
- Prior art keywords
- mixed oxide
- mixed
- producing
- puo
- 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.)
- Expired - Lifetime
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
- Monitoring And Testing Of Nuclear Reactors (AREA)
- Compositions Of Oxide Ceramics (AREA)
Description
【０００１】[0001]
【産業上の利用分野】本発明は、ＰｕＯ2 を含有する混
合酸化物燃料ペレットおよびその製造方法に関する。TECHNICAL FIELD The present invention relates to a mixed oxide fuel pellet containing PuO 2 and a method for producing the same.
【０００２】[0002]
【従来の技術】現在、ＰｕＯ2 とＵＯ2 との混合酸化物
（ＭＯＸ）燃料は、高速増殖炉，新型転換炉のみならず
軽水炉にも使用されつつあり、その需要は高くなってい
る。通常、ＭＯＸ燃料はＰｕＯ2 粉末とＵＯ2 粉末を機
械的に混合し、これを成形，焼結して得られるが、Ｐｕ
Ｏ2 とＵＯ2 との混合酸化物はＵＯ2 に比べ焼結性が低
く、同一焼結条件下では、その焼結ペレットの密度，結
晶粒径は共にＵＯ2 焼結ペレットよりも小さくなること
が一般に知られている。結晶粒径が小さいと核分裂生成
ガス（ＦＰガス）の拡散距離が小さくなり、燃焼中のＦ
Ｐガス放出率が大きくなる欠点がある。さらに、遊離Ｐ
ｕＯ2 が残存すると、燃焼中にプルトニウムの局所核分
裂によってＦＰガス放出が増大し、燃料の健全性が失わ
れるおそれがあることが指摘されている。 2. Description of the Related Art Currently, a mixed oxide (MOX) fuel of PuO 2 and UO 2 is being used not only in fast breeder reactors and new converters but also in light water reactors, and its demand is increasing. Usually, MOX fuel is obtained by mechanically mixing PuO 2 powder and UO 2 powder, molding and sintering the mixture.
The mixed oxide of O 2 and UO 2 has lower sinterability than UO 2 and both density and crystal grain size of the sintered pellet are smaller than that of UO 2 sintered pellet under the same sintering conditions. Is generally known. If the crystal grain size is small, the diffusion distance of the fission product gas (FP gas) becomes short, and the F
There is a drawback that the P gas release rate becomes large. Furthermore, free P
It has been pointed out that if uO 2 remains, the fission of FP gas may increase due to the local fission of plutonium during combustion, resulting in loss of fuel integrity.
【０００３】従来、均一な組織を有する、すなわちＵＯ
2 とＰｕＯ2 との固溶状態がよいペレットを製造する方
法として、共沈法によって製造したＵＯ2 −ＰｕＯ2 混
合粉末を使用する方法が用いられてきた。しかしこの方
法は、機械的に混合されたＵＯ2 −ＰｕＯ2 混合粉末を
用いる方法に比べて工程が複雑で費用がはるかに高くな
る欠点がある。Conventionally, it has a uniform structure, that is, UO.
As a method for producing a pellet in which 2 and PuO 2 are in a good solid solution state, a method using a UO 2 —PuO 2 mixed powder produced by a coprecipitation method has been used. However, this method has a drawback in that the process is complicated and the cost is much higher than the method using the mechanically mixed UO 2 -PuO 2 mixed powder.
【０００４】そこで、機械的に混合されたＵＯ2 −Ｐｕ
Ｏ2 混合粉末を用いて固溶状態のよいＭＯＸ燃料を得る
製造方法が提唱されている（特開昭55-82096号公報）。
この方法は、Ｐｕ+4をＰｕ+3に還元するのに充分低い酸
素ポテンシャルの下で焼結することを特徴としている。
しかしながら、低酸素ポテンシャル下で焼結すると、焼
結中にクラックが多数発生するので（Journal of Nucle
ar Materials, vol.106(1982年) P.181-190 参照）、ペ
レットの実効的な熱伝導率を低下させ、燃焼中のＦＰガ
ス放出率を増大させるという問題がある。Therefore, mechanically mixed UO 2 -Pu
A manufacturing method for obtaining a MOX fuel having a good solid solution state by using O 2 mixed powder has been proposed (JP-A-55-82096).
This method is characterized by sintering under a sufficiently low oxygen potential to reduce Pu +4 to Pu +3 .
However, if sintering is performed under a low oxygen potential, many cracks will occur during sintering (Journal of Nucleus
ar Materials, vol.106 (1982) P.181-190), there is a problem that the effective thermal conductivity of the pellet is lowered and the FP gas release rate during combustion is increased.
【０００５】[0005]
【発明が解決しようとする課題】本発明はかかる問題に
対処してなされたもので、固溶状態がよく、かつＦＰガ
ス放出率の増大を避けることのできるＭＯＸ燃料ペレッ
トを提供することを目的とし、さらにその製造方法を提
供することを目的とするものである。SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a MOX fuel pellet having a good solid solution state and capable of avoiding an increase in the FP gas release rate. The present invention further aims to provide a manufacturing method thereof.
【０００６】[0006]
【課題を解決するための手段】すなわち、本発明は遊離
ＰｕＯ2 相が残存しておらず、ＵＯ2 粒子と（Ｕ，Ｐ
ｕ）Ｏ2 粒子がそれぞれ20〜40μm の範囲内の平均結晶
粒径を有し、その結晶粒界のほとんどが核燃料体の全重
量を基準として 40ppm以上 0.1wt％未満の割合を占める
ガラス状もしくは結晶質性のアルミナシリケート相で被
覆されていることを特徴とする混合酸化物燃料ペレット
に関し、さらにその製造方法として、ＵＯ2 とＰｕＯ2
とを含有する混合酸化物粉末を圧縮成形した後焼結する
核燃料ペレットの製造方法において、混合酸化物に50wt
％より多く80wt％以下であるＳｉＯ2 と残部のＡｌ2 Ｏ
3 とから成る組成を有する焼結剤を、混合酸化物と該焼
結剤との合計量を基準として 40ppm以上 0.1wt％未満の
割合で混合して混合物を調製し、これを成形して圧縮体
とした後、約1500℃〜約1800℃の範囲内の温度で弱酸化
性雰囲気中において前記圧縮体を焼結することを特徴と
する混合酸化物燃料ペレットの製造方法に関する。That is, according to the present invention, free PuO 2 phase does not remain, and UO 2 particles and (U, P
u) O 2 particles each have an average crystal grain size within the range of 20 to 40 μm, and most of the crystal grain boundaries account for 40 ppm or more and less than 0.1 wt% of the total weight of the nuclear fuel body, or glassy or A mixed oxide fuel pellet characterized by being coated with a crystalline alumina silicate phase, and as a method for producing the same, UO 2 and PuO 2
In a method for producing a nuclear fuel pellet, in which a mixed oxide powder containing and is compression molded and then sintered, 50 wt% of mixed oxide is added.
% And 80 wt% or less of SiO 2 and the balance of Al 2 O
A sinter having a composition consisting of 3 and 3 is mixed at a ratio of 40 ppm or more and less than 0.1 wt% based on the total amount of the mixed oxide and the sinter to prepare a mixture, which is molded and compressed. The present invention relates to a method for producing mixed oxide fuel pellets, which comprises sintering the compressed body in a weakly oxidizing atmosphere at a temperature in the range of about 1500 ° C to about 1800 ° C after forming the body.
【０００７】[0007]
【作用】本発明の製造方法によれば、焼結剤として添加
したＳｉＯ2 とＡｌ2 Ｏ3 とが約1500℃〜1800℃の焼結
温度において一液相の共融体となり、この液相を介して
ＰｕＯ2 がペレット全域に分散し、ＵＯ2 とＰｕＯ2 と
の実効的な拡散距離が小さくなって固溶相の生成が促進
され、遊離ＰｕＯ2 相が消失する。さらに、液相焼結メ
カニズムによって核燃料粉末間の表面反応を促進し、結
晶粒の成長を助長する。According to the manufacturing method of the present invention, SiO 2 and Al 2 O 3 added as the sintering agent become a one-liquid phase eutectic at a sintering temperature of about 1500 ° C. to 1800 ° C. The PuO 2 is dispersed throughout the pellets via the, the effective diffusion distance between UO 2 and PuO 2 is reduced, the generation of the solid solution phase is promoted, and the free PuO 2 phase disappears. Furthermore, the liquid phase sintering mechanism promotes the surface reaction between the nuclear fuel powders and promotes the growth of crystal grains.
【０００８】したがって本発明で得られたＭＯＸ燃料ペ
レットは、固溶状態が均一であり、遊離ＰｕＯ2 相が残
存せず、さらに結晶粒が大きいという特徴を有してい
る。遊離ＰｕＯ2 相が残存していないので、プルトニウ
ムの局所核分裂によるＦＰガス放出の増大を避けること
ができ、また、結晶粒が大きいので、ＦＰガスの結晶粒
界への拡散距離が増加し、ペレットからのＦＰガス放出
率が低下する。さらに、上記組成の焼結剤を添加したこ
とにより、結晶粒界に軟化温度が低い第二相が形成さ
れ、ペレットのクリープ特性が向上して耐ＰＣＩ（ペレ
ット被覆相互作用）性を向上させる。Therefore, the MOX fuel pellets obtained by the present invention are characterized in that the solid solution state is uniform, no free PuO 2 phase remains, and the crystal grains are large. Since the free PuO 2 phase does not remain, it is possible to avoid the increase in FP gas release due to the local fission of plutonium, and since the crystal grains are large, the diffusion distance of the FP gas to the grain boundaries is increased, and the pellet The FP gas release rate from the fuel cell is reduced. Further, by adding the sintering agent having the above composition, the second phase having a low softening temperature is formed at the grain boundaries, the creep characteristics of the pellets are improved, and the PCI (pellet coating interaction) resistance is improved.
【０００９】なお、本発明において、アルミナシリケー
ト相を、核燃料体の全重量を基準として約 40ppm以上
0.1wt％未満の割合としたのは、平均結晶粒径20μm の
場合、その核燃料体の全結晶粒界を検出できる幅（約１
nm）のアルミナシリケート相で被覆するためには少なく
とも約 40ppm必要であることが計算で求められ、また、
約 0.1wt％以上アルミナシリケートを添加しても結晶粒
径の増大に有意な差がない上に、核燃料体の密度を小さ
くするという逆効果を示すことが実験的に確かめられた
からである。In the present invention, the alumina silicate phase is used in an amount of about 40 ppm or more based on the total weight of the nuclear fuel body.
The ratio of less than 0.1 wt% is set so that when the average crystal grain size is 20 μm, the width that can detect all grain boundaries of the nuclear fuel body (about 1
nm) to be coated with an alumina silicate phase of at least about 40 ppm is calculated, and
This is because it was experimentally confirmed that the addition of about 0.1 wt% or more of alumina silicate has no significant difference in the increase of the crystal grain size, and has the adverse effect of reducing the density of the nuclear fuel body.
【００１０】[0010]
【実施例】本発明による酸化物燃料ペレットの製造方法
の一実施例を図１により説明する。本実施例では、酸化
プルトニウム（ＰｕＯ2 ）の代りに、化学的性質が類似
しているために模擬燃料として一般に用いられている酸
化セリウム（ＣｅＯ2 ）を使用した。EXAMPLE An example of a method for producing oxide fuel pellets according to the present invention will be described with reference to FIG. In the present example, plutonium oxide (PuO 2 ) was used in place of cerium oxide (CeO 2 ) that is commonly used as a simulated fuel because of its similar chemical properties.
【００１１】酸化アルミニウム（Ａｌ2 Ｏ3 ）40wt％と
酸化ケイ素（ＳｉＯ2 ）60wt％とを粗混合し、これを８
％−Ｈ2 ／Ｎ2 混合ガス気流中2100℃まで加熱して溶融
させた後冷却し、均一なアルミナシリケートを得た。こ
れを粉砕して均一な粉末とした。Aluminum oxide (Al 2 O 3 ) 40 wt% and silicon oxide (SiO 2 ) 60 wt% were roughly mixed, and this was mixed with 8
A uniform alumina silicate was obtained by heating to 2100 ° C. in a% -H 2 / N 2 mixed gas stream to melt and then cooling. This was pulverized into a uniform powder.
【００１２】この混合粉末を焼結剤として図１に示す工
程図に従い、核燃料ペレットを製造した。すなわち、二
酸化ウラン（ＵＯ2 ）粉末に上記焼結剤を混合した後、
酸化セリウム（ＣｅＯ2 ）粉末を添加し、圧粉成形して
グリーンペレットとした。ＣｅＯ2 および上記焼結剤の
添加量は、ＵＯ2 ，ＣｅＯ2 および上記焼結剤の合計量
を基準として、ＣｅＯ2 が約3.27wt％、焼結剤が 0.025
wt％とした。次に、このグリーンペレットを湿性水素雰
囲気中で1750℃、４時間焼結した。Nuclear fuel pellets were produced according to the process chart shown in FIG. 1 using the mixed powder as a sintering agent. That is, after the above sintering agent is mixed with uranium dioxide (UO 2 ) powder,
Cerium oxide (CeO 2 ) powder was added and pressed into green pellets. The amount of CeO 2 and the above-mentioned sintering agent added is about 3.27 wt% of CeO 2 and 0.025% of the sintering agent based on the total amount of UO 2 , CeO 2 and the above-mentioned sintering agent.
wt%. Next, the green pellets were sintered at 1750 ° C. for 4 hours in a moist hydrogen atmosphere.
【００１３】以上の方法により製作した核燃料ペレット
の焼結密度および平均結晶粒径を、焼結剤を用いない場
合および焼結剤を多量に添加した場合に得られた核燃料
ペレットのそれと比較して以下に示す。 本実施例に従い製作されたペレットの結晶粒径は、焼結
剤を添加しなかったペレットより明らかに大きい。また
焼結剤を多量添加しても結晶粒径の増大に有意な差がな
い上に、焼結密度が小さくなった。 The sintering density and average crystal grain size of the nuclear fuel pellets produced by the above method are compared with those of the nuclear fuel pellets obtained without using the sintering agent and with adding a large amount of the sintering agent. It is shown below. The grain size of the pellets produced according to this example is clearly larger than the pellets without the addition of sintering agent. Also
Even if a large amount of sintering agent is added, there is no significant difference in the increase of crystal grain size.
In addition, the sintered density was reduced.
【００１４】次に、図２に焼結剤を 0.025wt％含むＵＯ
2 −3.27wt％ＣｅＯ2 ペレットの、また図３に焼結剤を
含まないＵＯ2 −3.27wt％ＣｅＯ2 ペレットの、それぞ
れの研磨エッチング後の顕微鏡で見た組織図を比較して
示す。これらの図から、本実施例によって製造されたペ
レットでは、遊離ＵＯ2 相（符号１で示す。顕微鏡写真
では青色であり、本図では斜線で示した）が非常に少な
く（２ vol％以下）、固溶状態の均一性が優れているこ
とが分る。Next, FIG. 2 shows UO containing 0.025 wt% of a sintering agent .
Of 2 -3.27wt% CeO 2 pellets, also of UO 2 -3.27wt% CeO 2 pellets containing no sintering agent 3 shows a comparison of the organization chart as seen under a microscope after each polishing etch. From these figures, the pellets produced according to this example have very few free UO 2 phases (denoted by reference numeral 1. It is blue in the micrograph and shown by the diagonal lines in this figure) (2 vol% or less). It can be seen that the uniformity of the solid solution state is excellent.
【００１５】なお、上記実施例では、焼結雰囲気ガスと
して湿性水素ガスを用いたが、一酸化炭素と二酸化炭素
の混合ガスを用いてもよい。また、焼結剤として酸化ア
ルミニウム粉末と酸化ケイ素粉末の混合粉末を用いても
よい。Although wet hydrogen gas is used as the sintering atmosphere gas in the above embodiment, a mixed gas of carbon monoxide and carbon dioxide may be used. Further, a mixed powder of aluminum oxide powder and silicon oxide powder may be used as the sintering agent.
【００１６】[0016]
【発明の効果】本発明のＭＯＸ燃料ペレットは、固溶状
態が均一であって遊離ＰｕＯ2 相が残存していないの
で、プルトニウムの局所核分裂によるＦＰガス放出の増
大を避けることができる。また結晶粒径が大きいのでＦ
Ｐガスの結晶粒界への拡散距離が増加し、ペレットから
のＦＰガス放出率を低下させることができる。さらに結
晶粒界に軟化温度が低い第二相を有するため、ペレット
のクリープ速度を向上させ、耐ＰＣＩ性を向上させるこ
とができる。INDUSTRIAL APPLICABILITY The MOX fuel pellet of the present invention has a uniform solid solution state and does not have a free PuO 2 phase, so it is possible to avoid an increase in FP gas release due to local fission of plutonium. Also, since the crystal grain size is large, F
The diffusion distance of P gas to the crystal grain boundary is increased, and the FP gas release rate from the pellet can be reduced. Furthermore, since the grain boundary has the second phase having a low softening temperature, the creep rate of the pellet can be improved and the PCI resistance can be improved.
【図１】本発明の一実施例を示す工程図。FIG. 1 is a process chart showing one embodiment of the present invention.
【図２】本発明による核燃料ペレットを顕微鏡で見た組
織図。FIG. 2 is a microscopic structure view of a nuclear fuel pellet according to the present invention.
【図３】従来の方法により得られた核燃料ペレットを顕
微鏡で見た組織図。 FIG. 3 reveals nuclear fuel pellets obtained by a conventional method .
Organization chart as seen through a microscope.
１…遊離ＵＯ2 相。1: Free UO 2 phase.
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 平１−193691（ＪＰ，Ａ) 特開 平３−146895（ＪＰ，Ａ) 特開 平２−242195（ＪＰ，Ａ) ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-1-193691 (JP, A) JP-A-3-146895 (JP, A) JP-A-2-242195 (JP, A)
Claims (2)
2 粒子と（Ｕ，Ｐｕ）Ｏ2 粒子がそれぞれ20〜40μm の
範囲内の平均結晶粒径を有し、その結晶粒界のほとんど
が核燃料体の全重量を基準として 40ppm以上 0.1wt％未
満の割合を占めるガラス状もしくは結晶質性のアルミナ
シリケート相で被覆されていることを特徴とする混合酸
化物燃料ペレット。1. Free PuO 2 phase does not remain and UO
The two particles and the (U, Pu) O 2 particles each have an average crystal grain size in the range of 20 to 40 μm, and most of the grain boundaries are 40 ppm or more and 0.1 wt% or less based on the total weight of the nuclear fuel body.
A mixed oxide fuel pellet, characterized in that it is coated with a glassy or crystalline alumina silicate phase which accounts for a full proportion.
物粉末を圧縮成形した後焼結する核燃料ペレットの製造
方法において、混合酸化物に50wt％より多く80wt％以下
であるＳｉＯ2 と残部のＡｌ2 Ｏ3 とから成る組成を有
する焼結剤を、混合酸化物と該焼結剤との合計量を基準
として 40ppm以上 0.1wt％未満の割合で混合して混合物
を調製し、これを成形して圧縮体とした後、約1500℃〜
約1800℃の範囲内の温度で弱酸化性雰囲気中において前
記圧縮体を焼結することを特徴とする混合酸化物燃料ペ
レットの製造方法。2. In a method for producing a nuclear fuel pellet, wherein a mixed oxide powder containing UO 2 and PuO 2 is compression molded and then sintered, SiO 2 and the balance of the mixed oxide are more than 50 wt% and 80 wt% or less. Al 2 O 3 is mixed with a sintering agent having a composition of 40 ppm or more and less than 0.1 wt% based on the total amount of the mixed oxide and the sintering agent to prepare a mixture. After molding into a compressed body, 1500 ℃ ~
A method for producing a mixed oxide fuel pellet, comprising sintering the compressed body in a weakly oxidizing atmosphere at a temperature within a range of about 1800 ° C.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3241253A JP2672420B2 (en) | 1991-09-20 | 1991-09-20 | Mixed oxide fuel pellet and method for producing the same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3241253A JP2672420B2 (en) | 1991-09-20 | 1991-09-20 | Mixed oxide fuel pellet and method for producing the same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0580174A JPH0580174A (en) | 1993-04-02 |
| JP2672420B2 true JP2672420B2 (en) | 1997-11-05 |
Family
ID=17071492
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP3241253A Expired - Lifetime JP2672420B2 (en) | 1991-09-20 | 1991-09-20 | Mixed oxide fuel pellet and method for producing the same |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2672420B2 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100521638B1 (en) * | 2002-10-02 | 2005-10-13 | 한국원자력연구소 | Uranium dioxide fuel containing SiO2-CaO-Cr2O3 and thereof method |
| FR2860638A1 (en) * | 2003-10-06 | 2005-04-08 | Commissariat Energie Atomique | PROCESS FOR MANUFACTURING PELLETS OF NUCLEAR FUEL BASED ON MIXED (U, PU) O2 OR (U, TH) O2 OXIDE FUEL |
| KR101104042B1 (en) * | 2009-09-28 | 2012-01-06 | 한국원자력연구원 | A fabrication method of nuclear fuel pallet for heavy water reactor using spent nuclear fuel |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4869866A (en) * | 1987-11-20 | 1989-09-26 | General Electric Company | Nuclear fuel |
| JPH0731265B2 (en) * | 1989-03-15 | 1995-04-10 | 原子燃料工業株式会社 | Manufacturing method of nuclear fuel pellets |
| JPH0731267B2 (en) * | 1989-10-31 | 1995-04-10 | 原子燃料工業株式会社 | Manufacturing method of nuclear fuel pellets |
-
1991
- 1991-09-20 JP JP3241253A patent/JP2672420B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0580174A (en) | 1993-04-02 |
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