JPS6023759Y2 - nuclear fuel rod - Google Patents
nuclear fuel rodInfo
- Publication number
- JPS6023759Y2 JPS6023759Y2 JP1979128070U JP12807079U JPS6023759Y2 JP S6023759 Y2 JPS6023759 Y2 JP S6023759Y2 JP 1979128070 U JP1979128070 U JP 1979128070U JP 12807079 U JP12807079 U JP 12807079U JP S6023759 Y2 JPS6023759 Y2 JP S6023759Y2
- Authority
- JP
- Japan
- Prior art keywords
- nuclear fuel
- pellet
- end plug
- fuel rod
- buckling
- 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
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)
Description
【考案の詳細な説明】
本考案は原子炉用燃料棒の改良に関腰更に詳しくは一定
限度以上の荷重が作用した際に座屈しうる部材を最下核
燃料ペレットと下部端栓との間に設けることにより、核
燃料棒を炉内滞在期間中、健全に維持できるようにした
核燃料棒に関するものである。[Detailed description of the invention] This invention is concerned with the improvement of fuel rods for nuclear reactors. This invention relates to a nuclear fuel rod that can be maintained in good health during its stay in a reactor.
従来より用いられている核燃料棒は、例えば第１図ａに
示されるように、外径７〜１７ｍｍ、肉厚０−５〜１．
Ｏｍｍ、全要約４−ｍ、の被覆管２内に通常ペレットと
称する二酸化ウラン焼結体等の核***性物質３を挿入し
、被覆管の両端をそれぞれ上部端栓１および下部端栓５
を用いて溶接等により気密に封じて製作され、このとき
上部端栓１とペレットスタックとの間に核***時の生皮
ガスによる燃料棒内圧上昇やペレットスタックの熱膨張
等を吸収するための空所４を設けるようになし、またそ
の空所にはペレットスタックを押圧するコイルスプリン
グ６を設け、主として原子炉内に装着される以前の取扱
いによるペレットの動揺を防止していた。Conventionally used nuclear fuel rods have an outer diameter of 7 to 17 mm and a wall thickness of 0-5 to 1.5 mm, as shown in FIG. 1a, for example.
A fissile material 3 such as sintered uranium dioxide, which is usually called a pellet, is inserted into the cladding tube 2 of Omm, total summary 4-m, and both ends of the cladding tube are connected to the upper end plug 1 and the lower end plug 5, respectively.
At this time, a space is created between the upper end plug 1 and the pellet stack to absorb the increase in internal pressure of the fuel rod due to rawhide gas during nuclear fission and the thermal expansion of the pellet stack. A coil spring 6 was provided in the space to press the pellet stack, mainly to prevent the pellet from shaking due to handling before being installed in the reactor.
ところで被覆管２とペレット３との間隙は、ペレットか
らの熱伝達を向上させるため燃料棒製作時で０．３ｍｍ
程度以下に狭める設計としており、しかも実際の原子炉
内ではペレットは被覆管より著しく高温となること、ペ
レットの方が熱膨張の程度は被覆管より大であること、
照射に伴ってペレット体積が増大することなどにより、
ペレット−被覆管間隙は更に狭くなる傾向にある。Incidentally, the gap between the cladding tube 2 and the pellets 3 was set to 0.3 mm during fuel rod manufacturing in order to improve heat transfer from the pellets.
Furthermore, in an actual reactor, the pellets will be at a significantly higher temperature than the cladding, and the thermal expansion of the pellets will be greater than that of the cladding.
Due to the increase in pellet volume with irradiation, etc.
The pellet-cladding gap tends to become even narrower.
一方、原子炉での使用にあたっては、ペレットの割れ“
かけ゛等により、ペレットは被覆管と少くとも部分的に
強く接触して、必ずしもペレットが被覆管内を長さ方向
に自由に移動し得るものではなく、前述の第１図ａの空
所４のみではペレットの熱膨張による軸方向スタック伸
長を十分に吸収することは困難であった。On the other hand, when used in nuclear reactors, pellet cracking
Due to the above-mentioned application, the pellets come into strong contact with the cladding tube at least partially, and the pellets cannot necessarily move freely in the length direction within the cladding tube. It was difficult to sufficiently absorb the axial stack elongation due to thermal expansion of the pellets.
他方、燃料棒はその中央部分での発熱量が大であり、従
ってペレット−被覆管は他の部分よりも中央部分におい
て強く接触することが予想され、このため原子炉再起動
時とか過出力運転のほか原子炉の急激な出力上昇時には
、ペレットスタットの約１７２の部分（燃料棒中央より
下部端栓側）の熱膨張を吸収することができず、過剰の
異常な応力が被覆管もしくは端栓接合部に作用し、燃料
棒破損に至る可能性が存在していた。On the other hand, a fuel rod has a large calorific value in its central part, and therefore the pellet-cladding is expected to come into contact more strongly in the central part than in other parts. In addition, when a nuclear reactor's output suddenly increases, the approximately 172 portions of the pellet stud (from the center of the fuel rod to the lower end plug side) cannot absorb the thermal expansion, and excessive abnormal stress is applied to the cladding tube or end plug. There was a possibility that this would affect the joints and lead to fuel rod failure.
この点を解消する従来の試みとして、第１図すのように
、ペレットスタック上部に設けた空所４と同様な空所４
′を下部端栓５とペレット３の間にも設け、コイルスプ
リング６′によりペレットの下向きの伸びを吸収する提
案もなされている。As a conventional attempt to solve this problem, as shown in FIG.
It has also been proposed that a coil spring 6' be provided between the lower end plug 5 and the pellet 3 to absorb the downward elongation of the pellet.
しかし、このような構造にては、コイルスプリングの弾
性が原子炉内の高温条件下で失われ、実質的なバネ機能
を燃料棒炉内滞在期間を通じて保持し得ないこと、更に
はスプリングの弾性が失われてスプリング長さが短かく
なった場合にはペレット間に空隙が生じ、局所的な燃料
棒出力の増大（ホット・スポット）を招いて安全上好ま
しくない。However, in such a structure, the elasticity of the coil spring is lost under the high temperature conditions inside the reactor, and the substantial spring function cannot be maintained throughout the stay of the fuel rod in the reactor. If the spring length is shortened due to the loss of fuel, air gaps will be created between the pellets, leading to a localized increase in fuel rod output (hot spots), which is unfavorable from a safety standpoint.
また燃料集合体中に多数並列されている燃料棒の各ペレ
ットスタット下部位置が不規則に短かくなることから、
炉心核特性の低下をきたすといった欠点を有し、依然と
して上述の燃料棒破損の可能性等不都合点を除去するも
のではなかった。In addition, since the lower position of each pellet stud of the fuel rods, which are arranged in large numbers in a fuel assembly, becomes irregularly shortened,
It has the disadvantage of deteriorating the core characteristics, and still does not eliminate the disadvantages such as the possibility of fuel rod breakage mentioned above.
これらの点に鑑み、本考案では下部端栓とペレットとの
間にコイルスプリングを介装することなく、直接、座屈
部材が介在されており、該座屈部材は中空短円筒状であ
ってその周壁部には薄肉部、切欠き溝、または開口部が
形成されていて、設定荷重を超える荷重が作用したとき
座屈して連続的に短縮変形するようにし、この短縮変形
によって過剰応力の一部あるいは全部を解放しようとす
るものであって、図面に示す実施例に基づいて詳述する
と、つぎのとおりである。In view of these points, in the present invention, a buckling member is directly interposed between the lower end plug and the pellet without interposing a coil spring, and the buckling member has a short hollow cylindrical shape. A thin wall part, a notch groove, or an opening is formed in the peripheral wall part, and when a load exceeding a set load is applied, it buckles and is continuously shortened, and this shortening deformation relieves excess stress. The details of the invention are as follows based on the embodiment shown in the drawings.
第２図ａには、下部端栓５とペレット３との間に介装さ
れる座屈部材７の一例が示されていて、円筒体の中間外
側面部分を曲率Ｒで切削し、中央部分を薄くすることに
より、設定荷重での座屈を期待する。FIG. 2a shows an example of the buckling member 7 interposed between the lower end plug 5 and the pellet 3, in which the middle outer surface part of the cylindrical body is cut with a curvature R, and the central part By making it thinner, we expect buckling at a set load.
中央部の最小肉厚を適宜変えることにより座屈荷重を自
由に設定することができること勿論である。Of course, the buckling load can be freely set by appropriately changing the minimum wall thickness of the central portion.
例えば５ＵＳ３０４鋼を用いて外径１４ＴｒｒＩｎφ、
内径８閣φ、高さ２４１Ｍｔの円筒体を作り、その中間
外側面部分を曲率Ｒの値が１６．３５７７１７７１およ
び１７．４５１１ｒＩｎとして切削（この場合の中央部
の最小肉厚はそれぞれ０．３ｒｒｒｍおよび０．５ｍｍ
） Ｌ、これに対応する座屈荷重を求めたところ、第２
図すのとおり、それぞれ４００に９および９００に９で
あった。For example, using 5US304 steel, the outer diameter is 14TrrInφ,
A cylindrical body with an inner diameter of 8 mm and a height of 241 Mt was made, and the middle outer surface part was cut with curvature R values of 16.35771771 and 17.4511rIn (in this case, the minimum wall thickness of the center part was 0.3rrrm and 17.4511rIn, respectively). 0.5mm
) L, and when the corresponding buckling load was calculated, the second
As shown in the figure, they were 9 in 400 and 9 in 900, respectively.
なお燃料棒端枠部破断強度は、材質、寸法、使用温度に
よって異なるが、大体２００〜１８００に９程度である
。Although the breaking strength of the fuel rod end frame varies depending on the material, size, and operating temperature, it is approximately 9 in 200 to 1800.
通常の予定された原子炉運転条件下においては原形を保
持しておるが、過剰応力によっては最小肉厚個所で座屈
させる座屈部材７の形状としては種々の変形が可能であ
る。Although the buckling member 7 retains its original shape under normal, planned nuclear reactor operating conditions, the shape of the buckling member 7, which buckles at the minimum thickness point depending on excessive stress, can be modified in various ways.
例えば第２図のくびれ個所が一箇所であったものを第３
図のように三箇所に設けたり、第４図の例では円筒体の
中央部に円周方向に切欠き溝８を設け、また第５図の例
では切欠き溝８に加えて４個の開口部９を高さ方向に穿
設し、更に第６図の例では開口部９をラセン状に設けた
りすることである。For example, if the constriction in Figure 2 was in one place, then
In the example shown in Fig. 4, notch grooves 8 are provided in the center of the cylinder in the circumferential direction, and in the example shown in Fig. 5, in addition to the notch grooves 8, four grooves are provided. The opening 9 is formed in the height direction, and in the example shown in FIG. 6, the opening 9 is formed in a spiral shape.
何れの場合も切欠き溝８や開口部９の各部寸法を適切に
選ぶことにより、座屈荷重を所定値に設定するとともに
、所望の座屈曲線で連続的に短縮変形させようとするも
のである。In either case, by appropriately selecting the dimensions of each part of the notch groove 8 and the opening 9, the buckling load can be set to a predetermined value, and the buckling force can be continuously shortened and deformed along a desired buckling curve. be.
かかる座屈部材７は第７図ａに示すように下部端栓５と
ペレット３の間にただ一個設置され、或いは第７図すの
ように２個重ねて設置するようにしてもよい。Only one buckling member 7 may be installed between the lower end plug 5 and the pellet 3 as shown in FIG. 7a, or two buckling members 7 may be installed one above the other as shown in FIG.
以上のように座屈部材７をペレット３と下部端栓５との
間に介在させた本願構成によれば、通常の運転時には座
屈部材７は原形を保持して剛的に支持するから、コイル
スプリングを用いた場合に生じる可能性のあるペレット
間の空隙を生じさせなくできる。According to the configuration of the present invention in which the buckling member 7 is interposed between the pellet 3 and the lower end plug 5 as described above, the buckling member 7 maintains its original shape and is rigidly supported during normal operation. It is possible to eliminate gaps between pellets that may occur when using a coil spring.
また燃料集合体中に多数並列されている燃料棒の各ペレ
ットスタック下部位置が不揃いになって炉心核特性の低
下をきたすこともない。In addition, the lower positions of the pellet stacks of the fuel rods arranged in large numbers in the fuel assembly do not become uneven, which prevents deterioration of the reactor core characteristics.
過剰応力が作用すると座屈部材７は座屈を生じてそれ迄
の保持長さを短縮し、これによって過剰応力の一部ある
いは全部を解放するから、被覆管や端栓接合部に無理な
応力を与えないで済む。When excessive stress is applied, the buckling member 7 will buckle and shorten its retention length, thereby releasing part or all of the excess stress, thereby eliminating undue stress on the cladding tube and end plug joint. You don't have to give it.
更に、座屈による短縮は連続的に生じ、燃料の出力変動
に伴う短縮変形は小きざみに生じるので、その上に積層
されている核燃料ペレットが急激に移動することもなく
、ペレットスタック下部位置の不揃いの程度を小さく抑
えうる。Furthermore, shortening due to buckling occurs continuously, and shortening deformation due to fluctuations in fuel output occurs in small increments, so the nuclear fuel pellets stacked on top of them do not move suddenly, and the lower part of the pellet stack The degree of irregularity can be kept small.
また異常運転状態に至った時には原子炉は停止されるが
、座屈部材が座屈しているか否かは一時的に原子炉から
取出された燃料の該部分をＸ線検査等により簡単に知る
ことができるといった利点も有する。In addition, when an abnormal operating state occurs, the reactor is shut down, but whether or not the buckling member is buckled can be easily determined by X-ray inspection of the part of the fuel temporarily removed from the reactor. It also has the advantage of being able to
【図面の簡単な説明】
第１図ａと第１図すは従来の核燃料棒の断面図、第２図
ａはこの考案で使用される座屈部材の一例を示す図、第
２図すはその座屈線図、第３図から第６図までは座屈部
材の変形例を示す図、第７図ａ及びｂは取付状態を示す
断面図である。
３・・・ペレット、５・・・下部端栓、７・・・座屈部
材。[Brief Description of the Drawings] Figures 1a and 1 are cross-sectional views of conventional nuclear fuel rods, Figure 2a is a diagram showing an example of the buckling member used in this invention, and Figure 2 is a cross-sectional view of a conventional nuclear fuel rod. The buckling diagrams, FIGS. 3 to 6 are views showing modified examples of the buckling member, and FIGS. 7a and 7b are sectional views showing the attached state. 3... Pellet, 5... Lower end plug, 7... Buckling member.
Claims (1)
と下部端栓とにより封入した核燃料棒において、最下核
燃料ペレットと下部端栓との間に、コイルスプリングを
介装することなく、直接、座屈部材が介在されており、
該座屈部材は中空短円筒状であってその周壁部には薄肉
部、切欠き溝、または開口部が形成されていて、設定荷
重を超える荷重が作用したとき座屈して連続的に短縮変
形するようにしたことを特徴とする核燃料棒。In a nuclear fuel rod in which a nuclear fuel pellet inserted into a fuel cladding tube is enclosed by an upper end plug and a lower end plug, directly between the lowermost nuclear fuel pellet and the lower end plug without interposing a coil spring, A buckling member is interposed,
The buckling member has a short hollow cylindrical shape, and has a thin wall, a notch, or an opening formed in its peripheral wall, and buckles when a load exceeding a set load is applied, resulting in continuous shortening deformation. A nuclear fuel rod characterized by:
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1979128070U JPS6023759Y2 (en) | 1979-09-18 | 1979-09-18 | nuclear fuel rod |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1979128070U JPS6023759Y2 (en) | 1979-09-18 | 1979-09-18 | nuclear fuel rod |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5544294U JPS5544294U (en) | 1980-03-22 |
| JPS6023759Y2 true JPS6023759Y2 (en) | 1985-07-15 |
Family
ID=29091410
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1979128070U Expired JPS6023759Y2 (en) | 1979-09-18 | 1979-09-18 | nuclear fuel rod |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS6023759Y2 (en) |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS4932555U (en) * | 1972-06-20 | 1974-03-22 |
-
1979
- 1979-09-18 JP JP1979128070U patent/JPS6023759Y2/en not_active Expired
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS4932555U (en) * | 1972-06-20 | 1974-03-22 |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5544294U (en) | 1980-03-22 |
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