【発明の詳細な説明】 （産業上の利用分野） 本発明は原子燃料集合体、特に加圧水型原子炉に用いら
れる上記燃料集合体に関するものである。TECHNICAL FIELD The present invention relates to a nuclear fuel assembly, and more particularly to the above-mentioned fuel assembly used in a pressurized water reactor.
（従来の技術） 従来、加圧水型原子炉に用いられる燃料集合体の構造は
一般に第５図に示すように上下に対向配置された上部ノ
ズル（１）と下部ノズル（２）間に上端部と下端部が夫
々同ノズルに支持されて制御棒案内管（３）が設けられ
ると共に、これに複数の支持格子（４）が固定されて多
数の燃料棒（５）が上下方向に並列状態で保持された構
造からなっている そして、上記のように構成された燃料集合体は原子炉容
器内の炉心に固定され使用されるとき、下部ノズル
（２）の流水孔を通って冷却水が並列された各燃料棒間
の間隙を上昇し、その間、冷却水が加熱されて爾後の発
電に供されている。(Prior Art) Conventionally, a structure of a fuel assembly used in a pressurized water reactor is generally such that an upper end portion is provided between an upper nozzle (1) and a lower nozzle (2) which are vertically opposed to each other as shown in FIG. Control rod guide tubes (3) are provided with their lower ends supported by the respective nozzles, and a plurality of support grids (4) are fixed to the control rod guide tubes (3) to hold a large number of fuel rods (5) in parallel in the vertical direction. When the fuel assembly constructed as described above is fixed to the core of the reactor vessel and used, cooling water is juxtaposed through the water flow holes of the lower nozzle (2). Further, the gap between the fuel rods rises, and during that time, the cooling water is heated and is used for subsequent power generation.
ところで上記の如き燃料集合体において、下部ノズルの
流水孔より流入した冷却水は往々にして燃料棒の下端部
において激しく乱れており、このため、冷却水中にご
み，金属片などの異物が混入すると、該異物は下部ノズ
ルの流水孔より冷却水と一緒に燃料集合体の中へ入り、
支持格子にトラップされ、そこで異物は冷却水により振
動し、周辺の燃料棒に損傷を与える。By the way, in the fuel assembly as described above, the cooling water flowing in from the water flow hole of the lower nozzle is often violently disturbed at the lower end portion of the fuel rod, and therefore, when foreign matters such as dust and metal pieces are mixed in the cooling water. , The foreign matter enters the fuel assembly together with the cooling water through the water flow hole of the lower nozzle,
The foreign matter is trapped in the support grid, where the foreign matter is vibrated by the cooling water and damages the surrounding fuel rods.
そこで、燃料集合体において、このような異物混入に対
する対策が考究され、その１つの策として第６図に示す
ように燃料棒（５）の下端部と、下部ノズル（２）の上
面との中間部分にスクリーン（９）を配設することが提
案されている。（特公昭64−6423号公報参照） （発明が解決しようとする課題） しかしながら、上記スクリーンを配設することは異物の
捕捉除去という点では有効であるが、反面、冷却水の流
れに対する抵抗を増し、圧損が増加するという問題を提
起する。Therefore, in the fuel assembly, a countermeasure against such foreign matter mixture has been studied, and as one of the countermeasures, as shown in FIG. 6, an intermediate portion between the lower end portion of the fuel rod (5) and the upper surface of the lower nozzle (2) is investigated. It has been proposed to provide a screen (9) on the part. (See Japanese Examined Patent Publication No. 64-6423) (Problems to be Solved by the Invention) However, although the provision of the screen is effective in capturing and removing foreign matter, on the other hand, resistance to the flow of cooling water is reduced. And raise the problem of increased pressure loss.
かくて、本発明は叙上の如き状況に対処し、異物の侵入
を制限することにより上記冷却水中への異物の侵入の機
会を少なくするのみならず、冷却水の流れに対する抵抗
を排除し、圧損上昇を阻止せしめることを目的とするも
のである。Thus, the present invention copes with the situation as described above, not only reduces the chance of foreign matter entering the cooling water by limiting the entry of foreign matter, but eliminates the resistance to the flow of cooling water, The purpose is to prevent an increase in pressure loss.
（課題を解決するための手段） 即ち、上記目的を達成する本発明の特徴は、前記燃料集
合体における最下部支持格子を下部ノズル上面へ下げ、
支持格子下面と下部ノズル上面とを密着させると共に、
支持格子の格子点を下部ノズル流水孔上に位置せしめた
ことにある。(Means for Solving the Problem) That is, the feature of the present invention for achieving the above object is to lower the lowermost support grid in the fuel assembly to the upper surface of the lower nozzle,
While closely contacting the lower surface of the support grid and the upper surface of the lower nozzle,
This is because the grid points of the support grid are located above the lower nozzle water flow holes.
なお、ここで密着とは厳密な意味で間隙のない状態であ
ることは勿論であるが、若干の間隙があっても実質上、
異物の流入阻止に影響のないものを包含することは云う
までもない。In addition, it is needless to say that the term “adhesion” means that there is no gap in a strict sense, but even if there is a slight gap, practically,
Needless to say, it includes those that do not affect the inflow of foreign matter.
（作用） 上記の如く最下部支持格子の格子点を下部ノズル流水孔
上に位置させることにより、下部ノズル流水孔を通過
し、燃料集合体へ侵入しようとする異物を支持格子の格
子点がトラップすることとなり、異物の燃料集合体への
侵入を制限する。(Operation) By locating the lattice point of the lowermost support grid on the lower nozzle water flow hole as described above, foreign matter that passes through the lower nozzle water flow hole and enters the fuel assembly is trapped by the lattice point of the support grid. Therefore, the invasion of foreign matter into the fuel assembly is restricted.
勿論、本発明により異物が100％トラップできるのでは
なく、トラップ可能な異物は、従来、燃料の中へ流入
し、支持格子でトラップされ、燃料棒に損傷を与えてい
たものに限られ、従来でも支持格子でトラップされるこ
とのなかった小さな寸法の異物についてはトラップされ
る可能性は小さい。Of course, according to the present invention, 100% of foreign substances can be trapped, and the foreign substances that can be trapped are limited to those that conventionally flowed into the fuel and were trapped by the support grid and damaged the fuel rods. However, it is unlikely to be trapped for small-sized foreign matters that were not trapped by the support grid.
しかし、燃料棒に損傷を与えていた異物は十分侵入を防
止することができる。However, the foreign matter that has damaged the fuel rod can be sufficiently prevented from entering.
しかも支持格子数は最下部の支持格子を下げるだけで変
更はないため、燃料集合体の圧損は何ら従来と変わらな
い。Moreover, since the number of supporting grids does not change only by lowering the lowermost supporting grid, the pressure loss of the fuel assembly is no different from the conventional one.
（実施例） 以下、更に添付図面により本発明の実施例を説明する。(Example) Hereinafter, an example of the present invention will be described with reference to the accompanying drawings.
第１図は本発明に係る燃料集合体の全体を示す概要図
で、上下に対向配置された上部ノズル（１）と下部ノズ
ル（２）間に上端部と下端部が夫々同ノズル（１）
（２）に支持されて制御棒案内管（３）が設けられてお
り、これに支持格子（４）が固定されて多数の燃料棒
（５）が並列状態で保持されていることは前記第５図に
示す従来の燃料集合体と別段、変わるところはないが、
支持格子（４）のうち、最下部の支持格子（4a）が下部
ノズル（２）の上面まで下がり、同支持格子（4a）の下
面が下部ノズル（２）の上面と密着した状態となって配
置されている。FIG. 1 is a schematic view showing the whole fuel assembly according to the present invention, in which the upper end and the lower end are respectively located between the upper nozzle (1) and the lower nozzle (2) which are vertically opposed to each other.
The control rod guide tube (3) is supported by (2), and the support grid (4) is fixed to the control rod guide tube (3) to hold a large number of fuel rods (5) in parallel. There is no difference from the conventional fuel assembly shown in Fig. 5,
The lowermost support grid (4a) of the support grid (4) is lowered to the upper surface of the lower nozzle (2), and the lower surface of the support grid (4a) is in close contact with the upper surface of the lower nozzle (2). It is arranged.
第２図及び第３図はかかる第１図構成の本発明燃料集合
体の要部をなす下部ノズル（２）近傍の詳細を示す拡大
図であり、燃料棒（５）を挿通する最下部を支持格子
（4a）下面が下部ノズル（２）の上面に密着状態となっ
ていて下部ノズル（２）の流水孔（６）上に最下部支持
格子（4a）の格子点（Ｐ）が位置することによって実質
的に流水孔（６）を制限している。FIGS. 2 and 3 are enlarged views showing details of the vicinity of the lower nozzle (2) which is a main part of the fuel assembly of the present invention having the structure shown in FIG. 1, and shows the lowermost portion through which the fuel rod (5) is inserted. The lower surface of the support grid (4a) is in close contact with the upper surface of the lower nozzle (2), and the grid point (P) of the lowermost support grid (4a) is located on the water flow hole (6) of the lower nozzle (2). This substantially limits the water flow holes (6).
この状態を更に第４図に従って説明すると、下部ノズル
の流水孔（６）上に支持格子（4a）の格子点（Ｐ）が位
置し、燃料棒（５）を支持格子（4a）の格子内で弾性支
持部（７）及び剛性支持部（８）によって支持している
が、このとき、流水孔（６）は互いに交叉する支持格子
の格子板によって通過する異物の大きさに制限を付して
おり、従って、従来、燃料の中へ流入し、燃料棒に損傷
を与えていた大きさの異物の通過を阻止している。This state will be further described with reference to FIG. 4. The grid point (P) of the support grid (4a) is located on the water flow hole (6) of the lower nozzle, and the fuel rod (5) is located inside the grid of the support grid (4a). Are supported by the elastic support portion (7) and the rigid support portion (8), but at this time, the water flow holes (6) limit the size of foreign matter passing by the lattice plates of the support lattice intersecting each other. Therefore, it prevents the passage of foreign matter of a size that has hitherto flowed into the fuel and damaged the fuel rods.
とは云え、第４図に示すように、寸法（Ａ）（Ｂ）以下
をもつ異物は流入孔（６）と格子板，燃料棒（５）によ
って区画される空間内を通過する大きさであり、このよ
うな異物の通過を100％阻止することは困難である。換
言すれば、本発明によってもなお燃料の中へ流入する可
能性のある異物は残るが、かかる異物は寸法が前記
（Ａ）（Ｂ）以下の極めて小さいものに限られ、これら
は支持格子でもトラップされる可能性が小さいものであ
り、燃料棒の損傷には殆ど影響を及ぼすことはない。However, as shown in FIG. 4, the foreign matter having the dimensions (A) and (B) or less has such a size as to pass through the space defined by the inflow hole (6), the lattice plate and the fuel rod (5). However, it is difficult to completely prevent the passage of such foreign matter. In other words, according to the present invention, the foreign matters that may still flow into the fuel remain, but the foreign matters are limited to those extremely small in size (A) and (B) or less, and even in the supporting grid. It is less likely to be trapped and has little effect on fuel rod damage.
かくして上記燃料集合体を用いることによって下部ノズ
ルの流水孔（６）を通過し、燃料集合体の燃料棒（５）
間隙へ侵入しようとする異物を支持格子の格子点（Ｐ）
がトラップすることになり、燃料棒に損傷を与えていた
異物の侵入は実質的に制限され、燃料集合体の健全性は
一段と確保される。Thus, by using the above fuel assembly, it passes through the water flow hole (6) of the lower nozzle, and the fuel rod (5) of the fuel assembly.
Foreign matter that tries to enter the gap is supported by the lattice point (P)
Are trapped, the entry of foreign matter that has damaged the fuel rods is substantially limited, and the integrity of the fuel assembly is further ensured.
（発明の効果） 本発明は以上のように燃料集合体の最下部支持格子を下
げ、その下面を下部ノズル上面に実質的に密着せしめた
ものであり、下部ノズル流水孔上に支持格子の格子点が
位置し、これが燃料集合体へ侵入しようとする異物をト
ラップすることになることから、従来、燃料の中へ流入
し、上部の支持格子でトラップされ、冷却水により振動
し燃料棒に損傷を与えていた異物の燃料集合体内への侵
入を制限し、従って、燃料棒の損傷の機会はなくなり、
燃料集合体の健全性を確保し、原子炉運転の効率をより
高める顕著な効果を奏する。(Effects of the Invention) The present invention is one in which the lowermost support grid of the fuel assembly is lowered as described above, and the lower surface thereof is substantially brought into close contact with the upper surface of the lower nozzle, and the grid of the support grid is provided on the lower nozzle water flow holes. Since a point is located and this traps foreign substances that try to enter the fuel assembly, it conventionally flows into the fuel, is trapped by the upper support grid, and is vibrated by cooling water to damage the fuel rod. Restricts the intrusion of foreign matter into the fuel assembly, thus eliminating the chance of fuel rod damage.
The soundness of the fuel assembly is ensured, and the remarkable effect of further increasing the efficiency of reactor operation is achieved.
しかも本発明は最下部支持格子を下げるだけでスクリー
ンの如き部材を必要とせず、また支持格子数を増加する
こともないので燃料集合体の圧損を高めることなく、従
来と変わらない冷却水の流れを確保し得る実効を有す
る。Moreover, the present invention does not require a member such as a screen only by lowering the lowermost support grid, and does not increase the number of support grids. Therefore, the cooling water flow is the same as the conventional one without increasing the pressure loss of the fuel assembly. Has an effect that can secure.
第１図は本発明に係る燃料集合体の全体を示す一部省略
概要図、第２図はその下部ノズル近傍における一部切欠
要部斜視図、第３図は更にその一部斜視図、第４図は流
水孔，支持格子及び燃料棒の位置関係を示す平面図、第
５図は従来の燃料集合体の全体を示す一部省略概要図、
第６図は既知の異物侵入防止構造例を示す下部ノズル近
傍の正面図である。 （１）……上部ノズル，（２）……下部ノズル，（４）
……支持格子，（4a）最下部支持格子，（５）……燃料
棒，（６）……流水孔，（Ｐ）……格子点，FIG. 1 is a partially omitted schematic view showing the entire fuel assembly according to the present invention, FIG. 2 is a partial cutaway perspective view in the vicinity of a lower nozzle thereof, and FIG. 3 is a partial perspective view thereof. FIG. 4 is a plan view showing the positional relationship among the water flow holes, the supporting grids and the fuel rods, and FIG. 5 is a partially omitted schematic view showing the entire conventional fuel assembly.
FIG. 6 is a front view of the vicinity of the lower nozzle showing a known foreign substance intrusion prevention structure example. (1) …… Upper nozzle, (2) …… Lower nozzle, (4)
…… Support grid, (4a) Bottom support grid, (5) …… Fuel rod, (6) …… Flow hole, (P) …… Grid point,
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.6 識別記号 庁内整理番号 ＦＩ 技術表示箇所 Ｇ２１Ｃ 3/32 ＧＤＰ Ｂ 3/30 ＧＤＰ Ｋ ＧＤＰ Ｒ─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl.6 Identification number Internal reference number FI Technical display location G21C 3/32 GDP B 3/30 GDP K GDP R
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1068190AJPH07119820B2 (en) | 1989-03-20 | 1989-03-20 | Nuclear fuel assembly |
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1068190AJPH07119820B2 (en) | 1989-03-20 | 1989-03-20 | Nuclear fuel assembly |
| Publication Number | Publication Date |
|---|---|
| JPH02247595A JPH02247595A (en) | 1990-10-03 |
| JPH07119820B2true JPH07119820B2 (en) | 1995-12-20 |
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1068190AExpired - LifetimeJPH07119820B2 (en) | 1989-03-20 | 1989-03-20 | Nuclear fuel assembly |
| Country | Link |
|---|---|
| JP (1) | JPH07119820B2 (en) |
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6131993A (en)* | 1984-07-24 | 1986-02-14 | 原子燃料工業株式会社 | Pressurized water reactor fuel assembly |
| Publication number | Publication date |
|---|---|
| JPH02247595A (en) | 1990-10-03 |
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