JPH0743487A - Nuclear fuel pellet - Google Patents
Nuclear fuel pelletInfo
- Publication number
- JPH0743487A JPH0743487A JP5189549A JP18954993A JPH0743487A JP H0743487 A JPH0743487 A JP H0743487A JP 5189549 A JP5189549 A JP 5189549A JP 18954993 A JP18954993 A JP 18954993A JP H0743487 A JPH0743487 A JP H0743487A
- Authority
- JP
- Japan
- Prior art keywords
- nuclear fuel
- gas
- pellet
- dispersed
- thermal expansion
- 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.)
- Pending
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)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は核***性物質を含む酸化
物よりなる核燃料ペレットに関し、さらに詳しく言う
と、特に高燃焼時において、核***生成ガス（ＦＰガ
ス）の放出率の抑制、核燃料ペレットのスエリングの軽
減、ペレット−被覆管相互作用（ＰＣＩ）の軽減の各効
果を有する核燃料ペレットに関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nuclear fuel pellet made of an oxide containing a fissionable material. More specifically, it suppresses the release rate of fission product gas (FP gas), especially at high combustion, and provides a nuclear fuel pellet. The present invention relates to a nuclear fuel pellet having effects of reducing swelling and reducing pellet-cladding interaction (PCI).
【０００２】[0002]
【従来の技術】軽水炉では、経済性向上のため核燃料の
高燃焼度化が進められているが、燃焼の伸長にともない
種々のＦＰガスが核燃料ペレット内に蓄積し、燃料の諸
特性に様々な影響を与える。例えばガス状のＦＰガスが
ペレット外部へ放出されると燃料棒の内圧が上昇する。
また、ペレット内部に析出したＦＰガス等に起因してペ
レットのスエリングが生じ、被覆管との間に相互作用力
をおよぼす。高燃焼時の燃料においては、特にペレット
からのＦＰガス放出率の増加、およびＰＣＩが問題とな
ってくる。2. Description of the Related Art In light water reactors, higher burnup of nuclear fuel is being promoted to improve economic efficiency, but various FP gases accumulate in the nuclear fuel pellets as the combustion progresses, and various fuel characteristics are varied. Influence. For example, when the gaseous FP gas is released to the outside of the pellet, the internal pressure of the fuel rod increases.
Further, swelling of the pellet occurs due to the FP gas or the like deposited inside the pellet, and an interaction force is exerted between the pellet and the cladding tube. In the case of fuel at high combustion, the increase in the FP gas release rate from the pellets and PCI become problems.
【０００３】核燃料ペレット中で生成したガス状ＦＰは
結晶粒内を拡散し、結晶粒界へ気泡として析出し、その
気泡が連結してＦＰガスが放出されると考えられてい
る。すなわち、ＦＰガス放出はＦＰガスの核燃料ペレッ
ト結晶粒内での拡散に律速される。したがって、ＦＰガ
ス放出率を低減する方法として、核燃料ペレットの結晶
粒を大きくすることで結晶粒内のＦＰガスの拡散距離を
長くする方法が考えられた。また、ＦＰガスの拡散は、
核燃料物質を含む酸化物の陽イオンの拡散と正の相関が
あるため、低原子価酸化物を核燃料ペレットに固溶させ
陽イオンの拡散係数を小さくする方法、ペレットの熱伝
導率を高くすることでペレット温度を低下させ陽イオン
の拡散係数を小さくする方法が考えられた。It is considered that the gaseous FP produced in the nuclear fuel pellets diffuses in the crystal grains and precipitates as bubbles at the crystal grain boundaries, and the bubbles are connected to release the FP gas. That is, the FP gas release is rate-controlled by the diffusion of the FP gas in the nuclear fuel pellet crystal grains. Therefore, as a method of reducing the FP gas release rate, a method of increasing the diffusion length of the FP gas in the crystal grains by enlarging the crystal grains of the nuclear fuel pellet has been considered. Also, the diffusion of FP gas is
Since there is a positive correlation with the diffusion of cations in oxides containing nuclear fuel materials, a method of reducing the diffusion coefficient of cations by solid-dissolving low-valent oxides in nuclear fuel pellets, and increasing the thermal conductivity of the pellets. The method of lowering the pellet temperature and decreasing the diffusion coefficient of cations was considered.
【０００４】以上に述べた方法は、いずれも核燃料ペレ
ットの結晶粒内でのＦＰガスの滞在時間を長くする方法
であるが、高燃焼度まで照射された核燃料ペレットでは
照射によってＦＰガスの拡散が促進されることがあり、
十分な効果が期待できない場合がある。したがって、結
晶粒内で生成されたＦＰガスが拡散せずにそのまま結晶
粒内に残留する核燃料ペレットが望まれる。All of the above-mentioned methods are methods of prolonging the residence time of FP gas in the crystal grains of the nuclear fuel pellet. However, in the nuclear fuel pellet irradiated to a high burnup, the FP gas is diffused by the irradiation. May be promoted,
It may not be possible to expect a sufficient effect. Therefore, a nuclear fuel pellet in which the FP gas generated in the crystal grains does not diffuse and remains in the crystal grains is desired.
【０００５】そのためのＦＰガスの捕捉場所としては結
晶粒内の気孔が考えられるが、約０．０１μｍ程度の大
きさの気孔は核***片の衝突によってマトリックス中に
空孔として分散され、結晶粒界に拡散すると考えられて
いる。一方、比較的大きな気孔は、核***片が気孔を横
切った際にマトリックスの一部がスパッタされ、気孔の
表面に空孔を多く含んで付着し、その空孔が粒界に拡散
すると考えられている。その結果、１〜２μｍ以下の大
きさの気孔は照射下でほとんど消滅してしまう。Porosity in the crystal grains is considered as a trapping place of the FP gas for that purpose, but the pores having a size of about 0.01 μm are dispersed as vacancies in the matrix due to collision of fission fragments, and the crystal grain boundaries. Is believed to spread. On the other hand, relatively large pores are thought to be that when fission fragments cross the pores, a part of the matrix is sputtered and many pores adhere to the surface of the pores, and the pores diffuse to grain boundaries. There is. As a result, pores having a size of 1 to 2 μm or less almost disappear under irradiation.
【０００６】[0006]
【発明が解決しようとする課題】本発明は、上記の状況
に対処してなされたもので、核燃料ペレットにおいて、
特に高燃焼時におけるＦＰガスの放出率を抑制し、ペレ
ットのスエリングを抑制することで、ＰＣＩを軽減し、
核燃料の健全性を保持することを目的とする。SUMMARY OF THE INVENTION The present invention has been made in response to the above situation, and in a nuclear fuel pellet,
In particular, by suppressing the release rate of FP gas during high combustion and suppressing pellet swelling, PCI is reduced,
The purpose is to maintain the integrity of nuclear fuel.
【０００７】[0007]
【課題を解決するための手段】上記の目的を達成するた
め、本発明では、核***性物質を含む酸化物よりなる核
燃料ペレットにおいて、燃焼中に生成するＦＰガスある
いは空孔を捕獲できる場所を核燃料ペレット内に分散さ
せるようにする。すなわち、本発明は、核***性物質を
含む酸化物よりなる核燃料ペレットにおいて、前記核分
裂性物質を含む酸化物よりも熱膨張率の高い物質が前記
酸化物の結晶粒中に分散析出しており、前記分散析出し
た物質の平均半径が約１００ｎｍ以下であることを特徴
とする。In order to achieve the above object, in the present invention, in a nuclear fuel pellet made of an oxide containing a fissile material, a location where the FP gas or vacancies generated during combustion can be captured is the nuclear fuel. Disperse in pellets. That is, the present invention, in a nuclear fuel pellets made of an oxide containing a fissile material, a material having a higher coefficient of thermal expansion than the oxide containing a fissile material is dispersed and precipitated in the crystal grains of the oxide, The average radius of the dispersed and deposited material is about 100 nm or less.
【０００８】[0008]
【作用】本発明の熱膨張率の高い物質が分散析出してい
るペレットは、核***性物質を含む酸化物とそれよりも
熱膨張率が高い物質とを混合して焼結することによって
得られる。このようにすると、焼結後に熱膨張率の違い
によって、核***性物質を含む酸化物と析出物質の界面
に微小な気孔あるいは界面結合の弱い部分が生成し、こ
れらの気孔あるいは界面結合の弱い部分にＦＰガスある
いは空孔を捕獲することができる。その結果、結晶粒界
へ析出するガス状ＦＰ量は低減し、したがってペレット
からのＦＰガス放出量を低減することができる。The pellet of the present invention in which a substance having a high coefficient of thermal expansion is dispersed and deposited is obtained by mixing and sintering an oxide containing a fissile material and a substance having a coefficient of thermal expansion higher than that. . By doing so, due to the difference in the coefficient of thermal expansion after sintering, minute pores or portions with weak interfacial bonding are generated at the interface between the oxide containing the fissile material and the deposited material, and these pores or portions with weak interfacial bonding are formed. It is possible to capture FP gas or vacancies. As a result, the amount of gaseous FP deposited on the crystal grain boundaries is reduced, and therefore the amount of FP gas released from the pellet can be reduced.
【０００９】析出粒子の大きさが小さければ、それだけ
一つの結晶粒内にある析出粒子の数が多くなり、上記効
果は高くなる。析出粒子の直径は１００ｎｍ以下が好ま
しい。ただし４ｎｍ以下になると熱伝導率が著しく低下
するおそれがあるので、約４ｎｍ以上が好ましい。The smaller the size of the deposited particles, the greater the number of the deposited particles in one crystal grain, and the higher the above effect. The diameter of the deposited particles is preferably 100 nm or less. However, if the thickness is 4 nm or less, the thermal conductivity may be remarkably reduced, so that the thickness is preferably about 4 nm or more.
【００１０】また、従来の核燃料ペレットでは、微小な
気孔は核***の際に空孔となり、粒界へ拡散し消滅する
が、本発明の核燃料ペレットでは析出物の周りの気孔が
空孔となり、結晶粒界に達する前に他の析出物に捕獲さ
れる。Further, in the conventional nuclear fuel pellet, the minute pores become vacancies at the time of nuclear fission and diffuse to the grain boundaries and disappear. However, in the nuclear fuel pellet of the present invention, the pores around the precipitates become vacancies and crystallize. It is captured by other precipitates before reaching the grain boundaries.
【００１１】[0011]
【実施例】以下、本発明の実施例を図面を参照して説明
する。図１は、本発明の一実施例である核燃料ペレット
の結晶粒の状態を模式的に示した図である。核***性物
質を含む酸化物よりなる結晶粒１の中には、平均半径で
約１００ｎｍ以下の大きさの高熱膨張率を有する物質２
が分散し、その周りに気孔３が分散している。Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram schematically showing a state of crystal grains of a nuclear fuel pellet which is an embodiment of the present invention. In a crystal grain 1 made of an oxide containing a fissile substance, a substance 2 having a high coefficient of thermal expansion having an average radius of about 100 nm or less is used.
Are dispersed, and the pores 3 are dispersed around them.
【００１２】かかる核燃料ペレットを原子炉に装荷して
燃焼させると、核燃料物質の燃焼にともないガス状ＦＰ
あるいは空孔が生成する。しかしガス状ＦＰあるいは空
孔は結晶粒１と高熱膨張率を有する物質２との界面ある
いは気孔３によって捕獲され、結晶粒界へ析出するガス
状ＦＰ量は低減し、ＦＰガス放出率を低減することがで
きる。When such nuclear fuel pellets are loaded into a nuclear reactor and burned, a gaseous FP is produced as the nuclear fuel material burns.
Alternatively, holes are generated. However, the gaseous FPs or vacancies are captured by the interface between the crystal grains 1 and the substance 2 having a high coefficient of thermal expansion or by the pores 3, and the amount of the gaseous FPs deposited at the grain boundaries is reduced and the FP gas release rate is reduced. be able to.
【００１３】核燃料ペレットの平均結晶半径をｒ
G （ｍ）、高熱膨張率を有する析出物の平均半径をｒP
（ｍ）、高熱膨張率を有する析出物の核燃料ペレット中
の容積割合をＰとすれば、ペレット断面において一つの
結晶粒内にある析出粒子の数Ｎは、 Ｎ＝Ｐ・（ｒG ／ｒP ） …(1) で近似される。例えば、ｒG ＝１０μｍ、ｒP ＝１０ｎ
ｍ、Ｐ＝０．０５とすると、ペレット断面における一つ
の結晶粒内には５０００個の析出粒子が存在する。この
場合、半径約５０ｎｍの範囲内に一つの析出粒子を含
む。析出粒子の半径が約１００ｎｍであれば、半径約
０．５μｍの範囲内に一つの析出粒子を含む。The average crystal radius of the nuclear fuel pellet is r
G (m), the average radius of precipitates having a high coefficient of thermal expansion is r P
(M), where P is the volume ratio of precipitates having a high coefficient of thermal expansion in the nuclear fuel pellet, the number N of precipitate particles in one crystal grain in the pellet cross section is N = P · (r G / r P )… (1) is approximated. For example, r G = 10 μm, r P = 10n
When m and P = 0.05, there are 5000 precipitated particles in one crystal grain in the pellet cross section. In this case, one deposited particle is included within a radius of about 50 nm. When the radius of the deposited particles is about 100 nm, one deposited particle is included within the radius of about 0.5 μm.
【００１４】本発明の核燃料ペレットを製造するには、
二酸化ウランより高熱膨張率を有する半径約１００ｎｍ
以下の大きさの粒子を二酸化ウラン粉末に均一に混合
し、成型して焼結すればよい。焼結後には熱膨張率の違
いによって、二酸化ウランと析出物質の界面に微小な気
孔あるいは界面結合の弱い部分が生成する。二酸化ウラ
ンより高熱膨張率を有する物質としては、核燃料酸化物
の焼結温度（１２００℃〜１８００℃）あるいはそれ以
上の温度範囲において融点を有する金属あるいはその化
合物が挙げられる。例えば、酸化マンガン、酸化ストロ
ンチウム、酸化カルシウム、コバルトおよびその酸化物
ならびにフッ化物、ニッケルおよびその酸化物、トリウ
ム、パラジウム、鉄およびその酸化物ならびにフッ化
物、バリウムおよびそのフッ化物、ストロンチウムフッ
化物、タングステン酸化物、リチウムアルミニウム酸化
物、リチウムタンタル酸化物、鉄チタン酸化物、ナトリ
ウムニオブ酸化物がある。このうち、核燃料酸化物の焼
結雰囲気で安定な物質として、特に、酸化マンガン、ニ
ッケル、鉄、パラジウムが望ましい。To produce the nuclear fuel pellets of the present invention,
Radius of about 100 nm with higher coefficient of thermal expansion than uranium dioxide
Particles having the following sizes may be uniformly mixed with uranium dioxide powder, molded, and sintered. After sintering, fine pores or weakly interfacial bonds are formed at the interface between the uranium dioxide and the deposited substance due to the difference in thermal expansion coefficient. Examples of the substance having a higher coefficient of thermal expansion than uranium dioxide include a metal or a compound thereof having a melting point at a sintering temperature (1200 ° C. to 1800 ° C.) of a nuclear fuel oxide or higher. For example, manganese oxide, strontium oxide, calcium oxide, cobalt and its oxides and fluorides, nickel and its oxides, thorium, palladium, iron and its oxides and fluorides, barium and its fluorides, strontium fluoride, tungsten. There are oxides, lithium aluminum oxides, lithium tantalum oxides, iron titanium oxides, and sodium niobium oxides. Of these, manganese oxide, nickel, iron, and palladium are particularly preferable as the stable substance in the sintering atmosphere of the nuclear fuel oxide.
【００１５】析出粒子の大きさは小さい方が好ましい
が、析出粒子の周りに生ずる気孔の平均直径が約４ｎｍ
以下になると核燃料ペレットの熱伝導率が著しく低下す
るおそれがあるため、析出粒子の大きさとしては、約４
ｎｍ以上のものが好ましい。The size of the deposited particles is preferably small, but the average diameter of the pores formed around the deposited particles is about 4 nm.
Since the thermal conductivity of the nuclear fuel pellets may be significantly reduced when the amount is below, the size of the deposited particles is about 4
Those having a thickness of nm or more are preferable.
【００１６】また、核***性物質を含む酸化物よりなる
結晶粒の大きさはできる限り大きい方が効果的である。
また、核***性物質の密度を低下させないためには、核
燃料ペレットの密度を向上させた方が好ましく、高熱膨
張率を有する物質の添加量としては核燃料ペレットの容
積分率として５％以下であることが好ましい。Further, it is effective that the size of the crystal grain made of an oxide containing a fissile material is as large as possible.
Further, in order not to reduce the density of the fissile material, it is preferable to improve the density of the nuclear fuel pellets, and the amount of addition of the material having a high coefficient of thermal expansion is 5% or less as the volume fraction of the nuclear fuel pellets. Is preferred.
【００１７】[0017]
【発明の効果】以上説明したように、本発明によれば、
核***性物質の燃焼により生成したガス状ＦＰを結晶粒
内に捕獲することができるので、ＦＰガス放出率を低減
することができ、特に高燃焼時において健全なペレット
を得ることができる。As described above, according to the present invention,
Since the gaseous FP generated by the combustion of the fissile material can be captured in the crystal grains, the FP gas release rate can be reduced, and a sound pellet can be obtained especially at the time of high combustion.
【図１】本発明の一実施例である核燃料ペレットの結晶
粒の状態を模式的に示した図。FIG. 1 is a view schematically showing a state of crystal grains of a nuclear fuel pellet which is an embodiment of the present invention.
１…核***性物質を含む酸化物、２…核***性物質を含
む酸化物より熱膨張率の高い物質、３…気孔。1 ... Oxide containing fissile material, 2 ... Material having higher thermal expansion coefficient than oxide containing fissile material, 3 ... Porosity.
Claims (1)
料ペレットにおいて、前記核***性物質を含む酸化物よ
りも熱膨張率の高い物質が前記酸化物の結晶粒中に分散
析出しており、前記分散析出した物質の平均半径が約１
００ｎｍ以下であることを特徴とする核燃料ペレット。1. In a nuclear fuel pellet made of an oxide containing a fissile material, a substance having a coefficient of thermal expansion higher than that of the oxide containing a fissile material is dispersed and precipitated in the crystal grains of the oxide. The average radius of the dispersed and deposited material is about 1
A nuclear fuel pellet characterized by having a size of 00 nm or less.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP5189549A JPH0743487A (en) | 1993-07-30 | 1993-07-30 | Nuclear fuel pellet |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP5189549A JPH0743487A (en) | 1993-07-30 | 1993-07-30 | Nuclear fuel pellet |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH0743487A true JPH0743487A (en) | 1995-02-14 |
Family
ID=16243183
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP5189549A Pending JPH0743487A (en) | 1993-07-30 | 1993-07-30 | Nuclear fuel pellet |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0743487A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1246203A1 (en) * | 2001-03-27 | 2002-10-02 | Framatome ANP GmbH | Method for manufacturing a nuclear fuel sintered body and nuclear fuel sintered body |
| US20130240805A1 (en) * | 2008-11-11 | 2013-09-19 | Korea Hydro & Nuclear Power Co., Ltd. | Uranium Dioxide Nuclear Fuel Containing Mn and Al as Additives and Method of Fabricating the Same |
-
1993
- 1993-07-30 JP JP5189549A patent/JPH0743487A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1246203A1 (en) * | 2001-03-27 | 2002-10-02 | Framatome ANP GmbH | Method for manufacturing a nuclear fuel sintered body and nuclear fuel sintered body |
| US6808656B2 (en) | 2001-03-27 | 2004-10-26 | Framatome Anp Gmbh | Method of producing a nuclear fuel sintered body |
| US20130240805A1 (en) * | 2008-11-11 | 2013-09-19 | Korea Hydro & Nuclear Power Co., Ltd. | Uranium Dioxide Nuclear Fuel Containing Mn and Al as Additives and Method of Fabricating the Same |
| US8989340B2 (en) * | 2008-11-11 | 2015-03-24 | Korea Atomic Energy Reseach Institute | Uranium dioxide nuclear fuel containing Mn and Al as additives and method of fabricating the same |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| RU2735243C2 (en) | Completely ceramic microencapsulated fuel, made with burnable absorber as a sintering intensifier | |
| US4566989A (en) | Burnable neutron absorbers | |
| JPS61134689A (en) | Nuclear reactor fuel rod aggregate | |
| US4474728A (en) | Neutron absorber pellets with modified microstructure | |
| US9653188B2 (en) | Fabrication method of burnable absorber nuclear fuel pellets and burnable absorber nuclear fuel pellets fabricated by the same | |
| JPH0743487A (en) | Nuclear fuel pellet | |
| JP2004309453A (en) | Nuclear fuel sinter containing tungsten metal mesh and its manufacturing method | |
| JPH1026684A (en) | Production of nuclear fuel pellet | |
| CA1100302A (en) | High performance nuclear fuel element | |
| JP3076058B2 (en) | Nuclear fuel pellet and method for producing the same | |
| JP2002181975A (en) | Fuel pellet, its manufacturing method, and its fuel element and fuel assembly | |
| JP4135976B2 (en) | Modified nuclear fuel for delaying RIM effect | |
| JPH0371674B2 (en) | ||
| JPH0694876A (en) | Nuclear fuel pellet | |
| JP2003167084A (en) | Nuclear fuel pellet, manufacturing method therefor, fuel element using the nuclear fuel pellet, and fuel assembly | |
| JPH01253694A (en) | Manufacture of nuclear fuel pellet | |
| JP2860615B2 (en) | Fuel assembly for plutonium firing | |
| JPH0316634B2 (en) | ||
| JPH0121476B2 (en) | ||
| JPH03249595A (en) | Nuclear fuel pellet | |
| JP2000292576A (en) | Nuclear fuel pellet and its manufacture and nuclear fuel element and nuclear fuel assembly | |
| JPH0761820A (en) | Production of nuclear fuel pellet | |
| JPH09127280A (en) | Production of nuclear fuel particle | |
| JPH0448296A (en) | Production of nuclear fuel pellet | |
| JP2001099971A (en) | Nuclear fuel pellet and its manufacturing method, and its fuel element and fuel assembly |