JPH07311291A - Fuel assembly - Google Patents

Fuel assembly

Info

Publication number
JPH07311291A
JPH07311291A JP6105607A JP10560794A JPH07311291A JP H07311291 A JPH07311291 A JP H07311291A JP 6105607 A JP6105607 A JP 6105607A JP 10560794 A JP10560794 A JP 10560794A JP H07311291 A JPH07311291 A JP H07311291A
Authority
JP
Japan
Prior art keywords
fuel
rod
diameter
poison
rods
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
Application number
JP6105607A
Other languages
Japanese (ja)
Other versions
JP3292587B2 (en
Inventor
Kiyoshi Ueda
精 植田
Ryohei Ando
良平 安藤
Toru Mitsutake
徹 光武
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Toshiba Corp
Itel Corp
Original Assignee
Toshiba Corp
Itel Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Toshiba Corp, Itel Corp filed Critical Toshiba Corp
Priority to JP10560794A priority Critical patent/JP3292587B2/en
Publication of JPH07311291A publication Critical patent/JPH07311291A/en
Application granted granted Critical
Publication of JP3292587B2 publication Critical patent/JP3292587B2/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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

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  • Monitoring And Testing Of Nuclear Reactors (AREA)

Abstract

PURPOSE:To provide a fuel assembly which can suppress exceeding of neutron multiplication rate and control the multiplication rate evenly for whole operation cycle, improve cooling characteristics and does not lead to complication of assembling and disassembling work. CONSTITUTION:A multitude of fuel rods 22 without burnable poison in the fuel, a plurality of fuel rods 23 with burnable poison W the fuel and at least one thick diameter water rod 26 having larger diameter than the fuel rods except for a certain length regions at both ends are arranged in a grid. A part of the poison rods 23 is larger than the diameter of fuel rods except for a certain length region at the both ends, and the components of inner part and peripheral part are the same or different in the thick diameter multiple region poison rods. At least one rod of these thick diameter multiple region poison rods 23 is arranged adjacent to the thick diameter water rod 26 and a multitude of fuel rods 22 are arranged to surround the group of the thick diameter water rod 26 and the adjacent thick diameter multiple region poison rods 23.

Description

【発明の詳細な説明】Detailed Description of the Invention

【０００１】[0001]

【産業上の利用分野】本発明は軽水炉に好適な燃料集合
体に関し、特に核特性、熱特性、水力特性、解体または
組み立て性、経済性等の向上を図った燃料集合体に関す
る。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel assembly suitable for a light water reactor, and more particularly to a fuel assembly having improved nuclear characteristics, thermal characteristics, hydraulic characteristics, dismantling or assembling ability, and economical efficiency.

【０００２】[0002]

【従来の技術】例えば沸騰水型原子炉（以下ＢＷＲと略
する）の燃料集合体では一般に、方形のチャンネルボッ
クスの中に多数の燃料棒が規則的に配列され、燃料棒間
を中性子減速材兼冷却材である水（以下、冷却水または
水と呼ぶ）が下方（上流）から上方（下流）に向かって
流れている。この流れとともに、冷却水は燃料棒で発生
した熱を奪うことによって沸騰し、生じた蒸気はタービ
ンへ導かれて発電に供される。2. Description of the Related Art For example, in a fuel assembly of a boiling water reactor (hereinafter abbreviated as BWR), generally, a large number of fuel rods are regularly arranged in a rectangular channel box, and a neutron moderator is provided between the fuel rods. Water (also referred to as cooling water or water), which also serves as a coolant, flows from below (upstream) to above (downstream). With this flow, the cooling water boils by taking away the heat generated in the fuel rods, and the generated steam is guided to the turbine for power generation.

【０００３】図２６ないし図２８は、最近実用化される
ようになったＢＷＲの燃料集合体を例示している。26 to 28 exemplify a BWR fuel assembly which has recently been put into practical use.

【０００４】図２６（Ａ）は燃料集合体１の縦断面図で
ある。この燃料集合体１は、可燃性毒物が添加された燃
料棒を含む多数の燃料棒２と水棒３とを複数のスペーサ
４、上流側結合部材としての下部タイプレート５及び下
流側結合部材としての上部タイプレート６により規則的
に配列した燃料バンドルを、チャンネルボックス７の内
部に収納した構成となっている。FIG. 26A is a vertical sectional view of the fuel assembly 1. The fuel assembly 1 includes a plurality of fuel rods 2 including a fuel rod to which a burnable poison is added and a water rod 3, a plurality of spacers 4, a lower tie plate 5 as an upstream side connecting member, and a downstream side connecting member. The fuel bundle regularly arranged by the upper tie plate 6 is housed in the channel box 7.

【０００５】燃料棒２は同図（Ｂ）に示すごとく、上下
端に密封式の端栓８，９を有する金属製の被覆管１０の
中に多数の燃料ペレット１１を収納して構成されてい
る。燃料棒２の断面は一般に円形で上下端栓８，９を除
いて一様な径を有し、しかも通常すべての燃料棒２の外
径は同一とされている。As shown in FIG. 1B, the fuel rod 2 is constructed by accommodating a large number of fuel pellets 11 in a metal cladding tube 10 having hermetically sealed end plugs 8 and 9. There is. The cross section of the fuel rod 2 is generally circular and has a uniform diameter except for the upper and lower end plugs 8 and 9, and usually all the fuel rods 2 have the same outer diameter.

【０００６】水棒３は初期のＢＷＲの燃料集合体では用
いられていなかったが、経済性の向上が大きな目標とな
り、そのため燃料の濃縮度が次第に高められるにしたが
って採用されるようになったものである。このような水
棒は、初めの段階では燃料棒と略等しい外径を有するも
のとして構成され１本設けられていた。そして次の段階
で２本に増加し、さらに次の段階で４本の燃料棒を外し
た空間を占める太径水棒（本発明では４セル水棒と呼ぶ
こともある）として大形化されてきている。The water rod 3 was not used in the fuel assemblies of the early BWRs, but a major goal was to improve the economical efficiency, so that it was adopted as the fuel enrichment gradually increased. Is. In the first stage, one such water rod was constructed and had an outer diameter substantially equal to that of the fuel rod. Then, in the next stage, the number of rods is increased to two, and in the next stage, it is enlarged into a large-diameter water rod (occasionally called a 4-cell water rod in the present invention) occupying a space where four fuel rods are removed. Is coming.

【０００７】燃料集合体の改良設計はさらに進行中であ
り、７本の燃料棒を外した空間に２本の太径水棒を採用
する場合や、９本の燃料棒を外した空間に１本の断面円
形あるいは正方形のさらに横断面積の大きい太径（本発
明では超太径と呼ぶこともある）の水棒を採用する場合
もみられるようになっている。このような太径ないし超
太径の水棒は冷却水に対して広い濡れ面積を有するた
め、冷却水の流れに対して比較的大きな圧力損失を生じ
ることが知られている。なお、本明細書では、特に必要
な場合を除き、太径および超太径水棒を総称して太径水
棒と呼ぶ。The improved design of the fuel assembly is in progress, and when two large diameter water rods are used in the space where seven fuel rods are removed, or one space is removed when nine fuel rods are removed. In some cases, a water rod having a large diameter (sometimes referred to as an ultra-large diameter in the present invention) having a larger cross-sectional area than a circular or square cross section of a book is adopted. It is known that such a large-diameter or ultra-large-diameter water rod has a wide wetting area for cooling water, and thus causes a relatively large pressure loss with respect to the flow of cooling water. In the present specification, the large-diameter water rod and the ultra-large-diameter water rod are collectively referred to as a large-diameter water rod unless otherwise required.

【０００８】図２６（Ｃ）に示す水棒３は前述の４セル
水棒の例である。この水棒３の上部と下部とは耐震問題
と前記冷却水の圧力損失問題を緩和するために一部小径
な構成となっている。なお、水棒３の内部には通水孔３
ａを介して炉水が導入出され、この炉水が沸騰しない程
度に緩やかに流れ、その炉水によって中性子が効果的に
減速されるようになっている。The water rod 3 shown in FIG. 26 (C) is an example of the above-mentioned 4-cell water rod. The upper part and the lower part of the water rod 3 have a partly small diameter in order to alleviate the problem of seismic resistance and the problem of pressure loss of the cooling water. In addition, inside the water rod 3, the water passage 3
Reactor water is introduced and discharged via a, the reactor water slowly flows to the extent that it does not boil, and the neutrons are effectively decelerated by the reactor water.

【０００９】図２７（Ａ）は水棒３の直径が大きい部分
の燃料集合体１の横断面を示し、同図（Ｂ）は細い部分
の同燃料集合体１の横断面を示している。FIG. 27 (A) shows a cross section of the fuel assembly 1 in a portion where the water rod 3 has a large diameter, and FIG. 27 (B) shows a cross section of the fuel assembly 1 in a thin portion.

【００１０】図２８は燃料バンドルの軸方向出力分布、
および冷却水沸騰に伴って発生する水蒸気（ボイド）の
割合の軸方向分布を、模式化した燃料集合体１と対比し
て示したものである。FIG. 28 shows the axial power distribution of the fuel bundle,
Also, the axial distribution of the proportion of water vapor (voids) generated with the cooling water boiling is shown in comparison with the schematic fuel assembly 1.

【００１１】燃料集合体１は同図（Ａ）に示すように、
例えば７個のスペーサ４（ＳＰ１〜ＳＰ７）と、上下の
タイプレート６，５（ＵＴＰ，ＬＴＰ）とにより、可燃
性毒物を燃料に添加した複数の燃料棒（本明細書では毒
物棒と呼ぶ）を含む多数の燃料棒と水棒とが、規則的に
配列されて一体化されている。The fuel assembly 1 is, as shown in FIG.
For example, by using seven spacers 4 (SP1 to SP7) and upper and lower tie plates 6, 5 (UTP, LTP), a plurality of fuel rods in which burnable poisons are added to the fuel (referred to as poison rods in this specification) A large number of fuel rods including water and water rods are regularly arranged and integrated.

【００１２】同図（Ｂ）に示す出力分布において、上部
と下部とが格段に低下しているのは、これらの部分の燃
料の濃縮度を中性子経済性向上の観点から大幅に低下さ
せているためであり、近年の好ましい設計とされてい
る。In the output distribution shown in FIG. 2B, the upper part and the lower part are markedly reduced, which is why the fuel enrichment in these parts is significantly reduced from the viewpoint of improving neutron economic efficiency. This is because it is a preferable design in recent years.

【００１３】同図（Ｃ）は出力運転中の代表的なボイド
割合の軸方向分布を示したものである。主として上方に
おいてボイド割合が高く、中性子の減速効果が低下して
いる。このため、上記のように、出力分布が上方で低下
傾向となる。FIG. 3C shows a typical axial distribution of void ratio during output operation. The void ratio is high mainly in the upper part, and the neutron moderating effect is reduced. Therefore, as described above, the output distribution tends to decrease upward.

【００１４】したがって、上方（下流側）において燃料
の一部を除去すれば、相対的に燃料に対する割合が増加
し、上方における出力の低下の程度を緩和することがで
きる。本発明者はこの点に着目し、短尺燃料棒（Part L
ength Rod:ＰＬＲ）の概念を特開昭５２−５０４９８号
公報等で既に開示している。ここで、短尺化した燃料棒
の下端は、短尺化していない通常の燃料棒（本明細書で
は長尺燃料棒あるいは通常燃料棒と呼ぶ）の下端と揃え
るため、上部（下流部）では燃料棒が欠落することにな
る。この空間は“Vanishing Rod ”と呼ばれることがあ
る（本明細書ではＶＲまたはＶＲ空間と呼ぶ）。このＶ
Ｒ空間の形成により、冷却水の圧力損失が大幅に緩和さ
れ、流れの外乱に対する圧力損失の変化も減少して、熱
水力学的安定性が向上し、その結果核的な安定性も向上
するメリットが生ずる。また、長尺燃料棒では冷却特性
が悪化するような場合、これを短尺化することにより冷
却特性の悪化を回避することもできる。さらに燃料棒の
短尺化により、原子炉停止時の未臨界度が深くなり、停
止余裕を大きくすることも可能となる。Therefore, if a part of the fuel is removed on the upper side (downstream side), the ratio of the fuel to the fuel is relatively increased, and the degree of decrease in the output on the upper side can be alleviated. The present inventor paid attention to this point, and
The concept of "ength rod (PLR)" has already been disclosed in Japanese Patent Laid-Open No. 52-50498. Here, since the lower end of the shortened fuel rod is aligned with the lower end of a non-shortened normal fuel rod (referred to as a long fuel rod or a normal fuel rod in this specification), the fuel rod at the upper portion (downstream portion) is Will be missing. This space is sometimes referred to as the "Vanishing Rod" (herein referred to as VR or VR space). This V
Due to the formation of the R space, the pressure loss of the cooling water is significantly alleviated, the change of the pressure loss due to the disturbance of the flow is also reduced, and the thermo-hydraulic stability is improved, and as a result, the nuclear stability is also improved. There are merits. Further, when the cooling characteristics of the long fuel rod deteriorate, the deterioration of the cooling characteristic can be avoided by shortening the length. Furthermore, by making the fuel rods shorter, the subcriticality at the time of reactor shutdown becomes deeper, and it becomes possible to increase the shutdown margin.

【００１５】[0015]

【発明が解決しようとする課題】しかしながら、ＶＲ空
間を形成した場合には、ＶＲ空間の下端位置で冷却水の
上昇流に偏りが生じ、一部の燃料棒の冷却特性が悪化す
る場合がある。However, when the VR space is formed, the upward flow of the cooling water is biased at the lower end position of the VR space, which may deteriorate the cooling characteristics of some of the fuel rods. .

【００１６】また冷却水は発熱していないチャンネルボ
ックスの内面に接して層を成すように流れる傾向があ
り、従って燃料棒の冷却水への寄与は少ないことが理解
される。換言すると、チャンネルボックス内面に接して
いる水を利用して冷却特性を改良し得る余地があること
が理解できる。Further, it is understood that the cooling water tends to flow in a layered manner in contact with the inner surface of the channel box which does not generate heat, so that the contribution of the fuel rods to the cooling water is small. In other words, it can be seen that there is room for improving the cooling characteristics by using the water in contact with the inner surface of the channel box.

【００１７】ところで、燃料経済性向上、すなわち燃料
の高燃焼度化の観点から、燃料棒内の核分裂性核種（フ
ィッサイル）濃度（ウラン燃料ではＵ−２３５の濃縮
度）を高めることは不可欠である。また、蓄積されてい
るプルトニウムをウランに添加した混合酸化物燃料（Ｍ
ＯＸ燃料）を効果的に採用することも最近重要な問題と
なってきている。From the viewpoint of improving the fuel economy, that is, increasing the burnup of the fuel, it is indispensable to increase the fissionable nuclide (Fissile) concentration in the fuel rod (U-235 enrichment in uranium fuel). . In addition, mixed oxide fuel (M with added accumulated plutonium to uranium)
The effective adoption of OX fuel) has recently become an important issue.

【００１８】このように燃料棒内の核分裂性核種濃度を
高めたり、ＭＯＸ燃料を採用した場合、燃料集合体の中
性子増倍率が過大となったり、毒物棒による中性子増倍
効果抑制作用が低下しやすくなったりするため、従来に
比して多数かつ高濃度の毒物棒を燃料集合体の中に配置
する必要性が高くなる。従って、過大となりがちな燃料
集合体の中性子増倍率を効果的に、しかも運転サイクル
全体に亘ってなるべく一様に抑制できる燃料集合体の設
計が望まれている。As described above, when the fissionable nuclide concentration in the fuel rod is increased or the MOX fuel is used, the neutron multiplication factor of the fuel assembly becomes excessive, and the effect of suppressing the neutron multiplication effect by the poison rod decreases. Since it becomes easier, it becomes more necessary to dispose a large number and a high concentration of poison rods in the fuel assembly as compared with the conventional case. Therefore, it is desired to design a fuel assembly that can effectively suppress the neutron multiplication factor of the fuel assembly, which tends to be excessive, and as uniformly as possible over the entire operation cycle.

【００１９】本発明はこのような事情に鑑みてなされた
もので、中性子増倍率の過大化を抑制しつつ、運転サイ
クル全体に亘って一様に増倍率を制御できるとともに、
冷却特性の改良が図れ、しかも解体や組立て作業の複雑
化を招くことのない燃料集合体を提供することを目的と
する。The present invention has been made in view of the above circumstances, and it is possible to uniformly control the multiplication factor over the entire operation cycle while suppressing the neutron multiplication factor from becoming excessive.
It is an object of the present invention to provide a fuel assembly which has improved cooling characteristics and which does not complicate disassembling and assembling work.

【００２０】[0020]

【課題を解決するための手段】前記の目的を達成するた
めに、請求項１記載の発明は、燃料に可燃性毒物を添加
しない多数の燃料棒と、燃料に可燃性毒物を添加した複
数の毒物棒と、両端部の一定長さ範囲を除き前記燃料棒
の径より大きい径を有する少なくとも１本の太径水棒と
を、複数のスペーサ、上流側結合部材及び下流側結合部
材を用いて格子状に配列し一体化して燃料バンドルとし
た燃料集合体において、前記毒物棒の一部は両端部の一
定長さ範囲を除き前記燃料棒の直径より大きくかつ内部
と外周部とで組成を同一または異にする太径多領域毒物
棒とし、この太径多領域毒物棒の少なくとも１本は前記
太径水棒に隣接して配置し、かつ前記太径水棒とそれに
隣接する前記太径多領域毒物棒との集団を取り囲む配置
で多数の燃料棒を配設したことを特徴とする。In order to achieve the above-mentioned object, the invention according to claim 1 comprises a large number of fuel rods in which no burnable poison is added to the fuel and a plurality of fuel rods in which the burnable poison is added to the fuel. Using a plurality of spacers, an upstream side connecting member and a downstream side connecting member, a poison rod and at least one large-diameter water rod having a diameter larger than the diameter of the fuel rod except for a certain length range at both ends are provided. In a fuel assembly that is arranged in a lattice and integrated into a fuel bundle, a part of the poison rod is larger than the diameter of the fuel rod except for a certain length range at both ends, and the composition is the same in the inside and the outside. Alternatively, different large-diameter multi-zone poison rods may be used, and at least one of the large-diameter multi-zone poison rods is arranged adjacent to the large-diameter water rod, and the large-diameter water rod and the large-diameter multi-zone adjacent thereto. A large number of fuel rods in an arrangement that surrounds a group with area poison rods And it said that it has set.

【００２１】請求項２記載の発明は、請求項１記載の燃
料集合体において、太径水棒は、その管肉部に可燃性毒
物を含有してなることを特徴とする。The invention according to claim 2 is the fuel assembly according to claim 1, characterized in that the large-diameter water rod contains a burnable poison in its tube wall portion.

【００２２】請求項３記載の発明は、請求項１記載の燃
料集合体において、太径多領域毒物棒の少なくとも一部
のものが、内部に冷却材を貫流させる冷却材貫流部を有
することを特徴とする。According to a third aspect of the present invention, in the fuel assembly according to the first aspect, at least a part of the large-diameter multi-region poison rod has a coolant flow-through portion through which the coolant flows. Characterize.

【００２３】請求項４記載の発明は、請求項１記載の燃
料集合体において、太径多領域毒物棒の少なくとも一部
のものに添加された可燃性毒物の濃度が、その太径多領
域毒物棒の内部において高く、外周部において低いこと
を特徴とする。According to a fourth aspect of the present invention, in the fuel assembly according to the first aspect, the concentration of the burnable poison added to at least a part of the large-diameter multi-region poison rod is the large-diameter multi-region poison. It is characterized by a high inside of the rod and a low outside.

【００２４】請求項５記載の発明は、請求項４記載の燃
料集合体において、太径多領域毒物棒の少なくとも一部
のものの内部に添加された可燃性毒物が硼素化合物であ
り、外周部に添加された可燃性毒物がガドリニウム化合
物であることを特徴とする。The invention according to claim 5 is the fuel assembly according to claim 4, wherein the combustible poison added to the inside of at least a part of the large-diameter multi-region poison rod is a boron compound, It is characterized in that the added burnable poison is a gadolinium compound.

【００２５】請求項６記載の発明は、請求項１記載の燃
料集合体において、太径水棒または太径多領域毒物棒の
少なくとも一部のものが、冷却材の流れの下流側から一
定長さ範囲に亘って細径化されており、その細径化され
た部分でその部分に隣接する燃料棒の核分裂性核種の濃
縮度が天然ウランのウラン２３５の濃縮度より高い部分
に、冷却材の流れを隣接燃料棒の方向へ偏流させる偏流
機構を有することを特徴とする。According to a sixth aspect of the present invention, in the fuel assembly according to the first aspect, at least a part of the large-diameter water rod or the large-diameter multi-region poison poison rod has a constant length from the downstream side of the coolant flow. The fuel rods adjacent to the portion where the concentration of the fissile nuclides is higher than that of uranium 235 of natural uranium in the portion where the diameter is reduced. It is characterized by having a drift mechanism that biases the flow of the fuel in the direction of the adjacent fuel rods.

【００２６】請求項７記載の発明は、燃料に可燃性毒物
を添加しない多数の燃料棒と、燃料に可燃性毒物を添加
した複数の毒物棒と、両端部の一定長さ範囲を除き前記
燃料棒の径より大きい径を有する少なくとも１本の太径
水棒とを、複数のスペーサ、上流側結合部材及び下流側
結合部材を用いて格子状に配列し一体化して燃料バンド
ルとし、この燃料バンドルを取り囲む配置で金属製のチ
ャンネルボックスを設けてなる燃料集合体において、前
記チャンネルボックスに面した位置に配置された燃料棒
または毒物棒は、冷却水の流れの下流側端から一定長さ
範囲に亘って細径化されており、その細径化された部分
でその部分に隣接する燃料棒の核分裂性核種の濃縮度が
天然ウランのウラン２３５の濃縮度より高い部分に、冷
却材の流れを隣接燃料棒の方向へ偏流させる偏流機構を
有することを特徴とする。According to a seventh aspect of the present invention, a large number of fuel rods in which no burnable poison is added to the fuel, a plurality of poison rods in which the burnable poison is added to the fuel, and the fuel except for a fixed length range at both ends are provided. At least one large-diameter water rod having a diameter larger than the diameter of the rod is arranged in a lattice using a plurality of spacers, an upstream side coupling member and a downstream side coupling member, and integrated into a fuel bundle. In a fuel assembly provided with a metal channel box in a surrounding arrangement, the fuel rod or poison rod arranged at a position facing the channel box is within a certain length range from the downstream end of the flow of cooling water. The flow of the coolant is directed to the part where the enrichment of the fissionable nuclides of the fuel rod adjacent to that part is higher than that of the uranium 235 of natural uranium. adjacent And having a drift mechanism to flow polarization in the direction of the charge bars.

【００２７】請求項８記載の発明は、請求項６または７
記載の燃料集合体において、太径多領域毒物棒の下流側
で細径化されスペーサと係合する部分、チャンネルボッ
クスに面した燃料棒または毒物棒の下流側で細径化され
スペーサと係合する部分、および太径水棒の下流側で細
径化されスペーサと係合する部分のうち、少くともいず
れかの部分に、細径化されていない部分の直径と略同じ
外径を持つ短尺管を装着したことを特徴とする。The invention according to claim 8 is the invention according to claim 6 or 7.
In the fuel assembly described in (1), a portion that is reduced in diameter on the downstream side of the large-diameter multi-region poison rod and engages with the spacer, and a portion that is reduced on the downstream side of the fuel rod or poison rod facing the channel box and engages with the spacer. A short length with an outer diameter that is approximately the same as the diameter of the non-thinned portion in at least one of the thinned portion and the portion that is made thinner on the downstream side of the large diameter water rod and engages with the spacer. It is characterized by being fitted with a tube.

【００２８】[0028]

【作用】請求項１記載の発明に係る燃料集合体によれ
ば、中性子束が高い位置に太径多領域毒物棒を配置する
ことにより、大きい中性子増倍率抑制効果が得られるよ
うになり、燃料に可燃性毒物を添加した構成の毒物棒の
本数が削減可能となる。この結果、燃料集合体内の出力
ピーキングの緩和が図れるとともに、プルトニウムをよ
り多く装荷でき、また太径水棒の周りに集まりがちな冷
却水の流れが調整され、燃料棒の冷却に効果的に活用さ
れるため、燃料の冷却特性が向上するようになる。According to the fuel assembly of the first aspect of the invention, the large neutron multiplication factor suppressing effect can be obtained by arranging the large diameter multi-region poison rod at a position where the neutron flux is high. It is possible to reduce the number of poison rods having a structure in which a burnable poison is added to the. As a result, the output peaking in the fuel assembly can be mitigated, more plutonium can be loaded, and the flow of cooling water that tends to collect around the large diameter water rod is adjusted, which is effectively used for cooling the fuel rod. Therefore, the cooling characteristic of the fuel is improved.

【００２９】請求項２記載の発明に係る燃料集合体によ
れば、熱中性子束が高くなる位置が太径となっている太
径水棒の管肉部に可燃性毒物を含ませているので、燃料
集合体の中性子増倍率抑制効果が大きくなる。さらに太
径水棒の外周部および内周部の水に面して表面積が従来
の毒物棒の表面積に比べて著しく大きいため、１本の毒
物入り太径水棒の中性子増倍率抑制効果は、従来の毒物
棒の数倍（例えば５倍）に及ぶ。したがって、その分だ
け通常の毒物棒の本数を低減することができ、代りに通
常の燃料棒を使用することができる。原子炉運転サイク
ルのうちで太径多領域毒物棒の中性子吸収作用が続いて
いる期間は太径水棒の中性子吸収作用は抑制されるた
め、その期間における中性子増倍率の過大な抑制効果は
大幅に緩和される。According to the fuel assembly of the second aspect of the present invention, since the pipe wall portion of the large diameter water rod in which the position where the thermal neutron flux becomes high has a large diameter contains the burnable poison. The effect of suppressing the neutron multiplication factor of the fuel assembly is increased. Furthermore, since the surface area of the large diameter water rod facing the water on the outer peripheral portion and the inner peripheral portion is significantly larger than the surface area of a conventional poison rod, the neutron multiplication suppressing effect of one large diameter water rod containing a poison is It is several times (for example, five times) the size of conventional poison sticks. Therefore, the number of normal poison rods can be reduced by that amount, and a normal fuel rod can be used instead. During the period in which the neutron absorption action of the large diameter multi-zone poison rod continues in the reactor operation cycle, the neutron absorption action of the large diameter water rod is suppressed, so the excessive suppression effect of the neutron multiplication factor during that period is significant. Is alleviated.

【００３０】そして、太径多領域毒物棒の中性子吸収作
用が弱まった頃に毒物入り太径水棒の中性子吸収作用が
発揮される。運転サイクルの終了時点の少し前では一般
に毒物作用は最小とされるが、その際は単に太径水棒と
して作用し、燃料集合体のサイクル末期において不足が
ちとなる中性子増倍効果を向上させることができる。な
お、設計条件によってはサイクル末期でも毒物作用を残
す事も可能である。Then, when the neutron absorbing action of the large diameter multi-region poison rod is weakened, the neutron absorbing action of the thick water rod containing the poison is exerted. Poisoning is generally minimized shortly before the end of the operating cycle, in which case it simply acts as a large diameter water rod to improve the neutron multiplication effect that tends to be insufficient at the end of the cycle of the fuel assembly. You can Depending on the design conditions, it is possible to leave the toxic effect even at the end of the cycle.

【００３１】請求項３記載の発明に係る燃料集合体によ
れば、太径多領域毒物棒の内部に冷却材すなわち炉水を
導入することで高速中性子が減速されて毒物に吸収され
やすい熱中性子となるため、燃料集合体の中性子増倍率
抑制効果が一段と増大される。According to the fuel assembly of the third aspect of the present invention, by introducing a coolant, that is, reactor water into the large-diameter multi-zone poison rod, the fast neutron is decelerated and the thermal neutron is easily absorbed by the poison. Therefore, the effect of suppressing the neutron multiplication factor of the fuel assembly is further increased.

【００３２】請求項４記載の発明に係る燃料集合体によ
れば、太径多領域毒物棒の内部の可燃性毒物濃度を外周
部のそれより高くすることで、まず運転サイクルの初期
の燃料集合体の中性子増倍率が特に高くなりがちな期間
において増倍率抑制作用を済ませた後、外周部の可燃性
毒物の中性子吸収作用が消滅し、内部の可燃性毒物が緩
やかに増倍率抑制作用を発揮することになる。すなわ
ち、本構成により燃料集合体の中性子増倍率の実効的な
値をほぼ一定に保つ作用が得られる。According to the fuel assembly of the fourth aspect of the present invention, the concentration of the burnable poison inside the large-diameter multi-zone poison rod is made higher than that at the outer peripheral portion, so that the fuel assembly at the beginning of the operation cycle is first obtained. After completing the multiplication suppression effect during the period when the body's neutron multiplication factor tends to be particularly high, the neutron absorbing effect of the burnable poison in the outer peripheral part disappears, and the internal burnable poison slowly exerts the multiplication suppression effect. Will be done. That is, with this configuration, the effect of keeping the effective value of the neutron multiplication factor of the fuel assembly substantially constant is obtained.

【００３３】請求項５記載の発明に係る燃料集合体によ
れば、太径多領域毒物棒を特定することにより、請求項
４記載の発明による作用が具体的に実現できる。ただ
し、内部に添加された硼素化合物ではＢ−１０のみが可
燃性毒物となるが、Ｂ−１０の中性子吸収断面積がＧｄ
−１５５やＧｄ−１５７のそれらに比べてかなり小さ
く、運転サイクル末期でも中性子吸収作用が緩やかに続
く場合が多いため、その特性を踏まえた設計が必要とな
る。According to the fuel assembly of the fifth aspect of the present invention, the action according to the fourth aspect of the invention can be specifically realized by specifying the large-diameter multi-region poison rod. However, in the boron compound added inside, only B-10 is a combustible poison, but the neutron absorption cross section of B-10 is Gd.
It is much smaller than those of -155 and Gd-157, and the neutron absorbing action often continues gently even at the end of the operation cycle, so it is necessary to design in consideration of its characteristics.

【００３４】請求項６記載の発明に係る燃料集合体によ
れば、細径化された部分に装着された冷却水偏流機構の
作用によって、太径水棒および太径多領域毒物棒近傍に
集まりがちな冷却水が周辺の燃料棒の方へ偏流するた
め、燃料の冷却効果が向上する。According to the fuel assembly of the sixth aspect of the present invention, by the action of the cooling water uneven flow mechanism attached to the narrowed portion, the fuel assembly collects in the vicinity of the large diameter water rod and the large diameter multi-region poison rod. Since the cooling water, which tends to occur, is unevenly distributed toward the fuel rods in the vicinity, the fuel cooling effect is improved.

【００３５】請求項７記載の発明に係る燃料集合体によ
れば、チャンネルボックスに面した一部の燃料棒あるい
は毒物棒のうち、冷却水の流れの下流側で燃料棒の熱的
余裕の少ない部分を細径化し、そこに冷却水偏流機構を
設けることにより、その冷却水偏流作用によってチャン
ネルボックス内面の冷却水が隣接燃料棒の方へ偏流さ
れ、請求項６の発明と同様に隣接燃料棒の冷却に寄与す
ることができる。なお、本明細書において、「チャンネ
ルボックス」はＢＷＲ用燃料集合体のチャンネルボック
スに限らず、各種原子炉において燃料バンドルを直接的
に取り巻く構造材を広く示すものとする。According to the fuel assembly of the seventh aspect of the invention, among some of the fuel rods or poison rods facing the channel box, the fuel rod has a small thermal margin downstream of the flow of the cooling water. By narrowing the diameter of the portion and providing a cooling water non-uniform flow mechanism therein, the cooling water on the inner surface of the channel box is non-uniformly flowed toward the adjacent fuel rods by the cooling water non-uniform flow action, and the adjacent fuel rods are the same as the invention of claim 6. Can contribute to cooling. In the present specification, the “channel box” is not limited to the channel box of the BWR fuel assembly, but broadly refers to the structural material that directly surrounds the fuel bundle in various nuclear reactors.

【００３６】請求項８記載の発明に係る燃料集合体によ
れば、太径多領域毒物棒、燃料棒、毒物棒または太径水
棒の下流側の細径化されスペーサと係合する部分に、上
流側で細径化していない部分とほぼ同じ直径の短尺管が
装着されているため、スペーサ自体も特に変更する必要
がなく、また燃料集合体の組み立てや必要時の解体作業
の場合でも、従来とほぼ同様に作業を行うことができ
る。According to the fuel assembly of the eighth aspect of the present invention, the portion of the large diameter multi-region poison rod, the fuel rod, the poison rod or the thick water rod downstream of the thin portion which engages with the spacer is reduced. Since a short tube with the same diameter as the part that has not been thinned on the upstream side is installed, it is not necessary to change the spacer itself, and even when assembling the fuel assembly or disassembling work when necessary, The work can be performed almost in the same manner as in the past.

【００３７】なお、短尺管の上流側と下流側とにテーパ
を施すことにより、冷却特性の改良を行うことができ
る。例えば、細径化されている部分と短尺管との間を円
錐状に外径が滑らかにつながるようにテーパ部を設ける
ことにより、スペーサ部での流路面積変化が滑らかとな
り、流れに対する外乱を抑制することができる。また、
テーパ部により冷却水が近隣の長尺燃料棒に振り向けら
れるので、長尺燃料棒の冷却効率が改善される。必要で
あれば、短尺管部分などにおいて冷却水の旋回方向を逆
転させ、不必要な冷却水旋回の反動として生じる回転応
力を相殺させることもできる。The cooling characteristics can be improved by tapering the upstream side and the downstream side of the short tube. For example, by providing a taper part so that the outer diameter is smoothly connected in a conical shape between the narrowed portion and the short tube, the flow passage area change in the spacer part becomes smooth, and the disturbance to the flow is prevented. Can be suppressed. Also,
Since the cooling water is directed to the adjacent long fuel rods by the tapered portion, the cooling efficiency of the long fuel rods is improved. If necessary, the swirling direction of the cooling water can be reversed in the short pipe portion or the like to cancel the rotational stress generated as a reaction of the unnecessary swirling of the cooling water.

【００３８】[0038]

【実施例】以下、本発明に係る燃料集合体の実施例を図
面を参照して説明する。Embodiments of the fuel assembly according to the present invention will be described below with reference to the drawings.

【００３９】図１ないし図９は第１の実施例を示してい
る。1 to 9 show a first embodiment.

【００４０】この実施例の燃料集合体２０はＢＷＲ用燃
料集合体であり、図１および図２（Ａ）〜（Ｅ）に示す
ように、方形のチャンネルボックス２１の内部に、通常
の燃料棒（長尺燃料棒）２２と、これと外径がほぼ等し
い可燃性毒物棒２３（符号Ｇを付したもの。以下、Ｇ毒
物棒と呼ぶ。通常ガドリニア（Ｇｄ2 Ｏ3 ）をウラニア
（ＵＯ2 ）に添加して焼結したペレット２４が通常の燃
料棒と同様に金属管２５の中に充填されている（図２
（Ａ）））と、太径水棒２６（図２（Ｂ））と、中実太
径２領域毒物棒２７（図２（Ｃ））と、中水太径２領域
毒物棒２８（図２（Ｄ））と、チャンネルボックス２１
の内面に面した一部の偏流機構付き短尺燃料棒２９（図
２（Ｅ））（本明細書では偏流短尺燃料棒と呼ぶ）と
が、燃料バンドルコーナと中央とに規則的に配置されて
いる。The fuel assembly 20 of this embodiment is a BWR fuel assembly, and as shown in FIGS. 1 and 2A to 2E, a normal channel rod 21 is provided inside a rectangular channel box 21. (Long fuel rod) 22 and combustible poison rod 23 having the same outer diameter as that of the rod (marked with G. Hereinafter referred to as G poison rod. Ordinary gadolinia (Gd 2 O 3 ) is replaced with urania (UO 2 ) And sintered pellets 24 are filled in a metal tube 25 like a normal fuel rod (Fig. 2).
(A))), a large diameter water rod 26 (Fig. 2 (B)), a solid large diameter 2 area poison rod 27 (Fig. 2 (C)), and a medium water large diameter 2 area poison rod 28 (Fig. 2 (D)) and the channel box 21
A part of the short-length fuel rod 29 (FIG. 2 (E)) with a non-uniform flow mechanism facing the inner surface of the fuel cell (referred to as a short-flow non-uniform fuel rod in this specification) is regularly arranged at the fuel bundle corner and the center. There is.

【００４１】太径水棒２６は図２（Ｂ）に示すように、
外管２６ａと内管２６ｂとで２重管構造とされ、両者の
間にはガドリニウム（Ｇｄ）筒２６ｃが水密状に挿入さ
れている。内管２６ｂの内側には冷却材貫流部としての
通水孔２６ｄを介して炉水が矢印ａで示すように、下方
から上方へ沸騰しない程度に緩やかに流れている（この
可燃性毒物であるＧｄを添加した太径水棒２６を、以
下、毒物入り太径水棒と呼ぶ。） 中実太径２領域毒物棒２７は図２（Ｃ）に示すように、
外管２７ａと内管２７ｂとで２重構造とされ、外管２７
ａと内管２７ｂとの間にはガドリニアの添加割合が低い
（例えば１〜３重量％）円環状毒物ペレット２７ｃが、
また内管２７ｂの内部にはガドリニア添加割合が高い
（例えば５重量％以上）芯毒物ペレット２７ｄが、それ
ぞれ密封挿入されている。なお、内管２７ｂは省略して
もよい。芯毒物ペレット２７ｄは円環状ペレット２７ｃ
と比べて断面積が大幅に小さくなっており、ウランなど
の燃料物質を充填しなくても炉心への燃料装荷量の低下
率は微小であり、従って必要であればウラニアを用い
ず、ガドリニアを単独で、又はジルコニウム等を用いた
サーメットとして、或いはアルミナ（Ａｌ2 Ｏ3 ）やジ
ルコニア（ＺｒＯ2 ）等との混合酸化物焼結体として内
管の内部に充填される（ここで、ペレット状とは粒状も
含むものとする）。As shown in FIG. 2B, the large diameter water rod 26 is
The outer tube 26a and the inner tube 26b have a double tube structure, and a gadolinium (Gd) tube 26c is watertightly inserted therebetween. Inside the inner pipe 26b, reactor water flows gently through a water passage hole 26d as a coolant flow-through portion, as shown by an arrow a, so that it does not boil from below to above (this burnable poison is a burnable poison). The large-diameter water rod 26 to which Gd is added is hereinafter referred to as a large-diameter water rod containing poison.) The solid large-diameter two-region poison rod 27 is, as shown in FIG.
The outer pipe 27a and the inner pipe 27b have a double structure,
The annular poison pellet 27c having a low gadolinia addition rate (for example, 1 to 3% by weight) is provided between the a and the inner pipe 27b.
Further, inside the inner tube 27b, core poison pellets 27d with a high gadolinia addition ratio (for example, 5% by weight or more) are hermetically inserted. The inner pipe 27b may be omitted. The core poison pellet 27d is an annular pellet 27c.
The cross-sectional area is significantly smaller than that of, and the rate of decrease in the amount of fuel loaded into the core is small even without filling with fuel substances such as uranium. Therefore, if necessary, without using urania, using gadolinia It is filled inside the inner tube either alone or as a cermet using zirconium or as a mixed oxide sintered body with alumina (Al 2 O 3 ) or zirconia (ZrO 2 ) (here, pelletized And also include granular).

【００４２】中水太径２領域毒物棒２８は図２（Ｄ）に
示すように、中実太径２領域毒物棒２７と同様に外管２
８ａ、内管２８ｂ、円環状毒物ペレット２８ｃを有する
構成であるが、芯毒物ペレットがなく、内管２８ｂの内
部に炉水を矢印ｂのように通水孔２８ｄを介して沸騰し
ない程度に流す点で異なっている。内管２８ｂの内径を
大きくすると、毒物棒としての反応度効果が増大する代
わりに早期に燃焼し尽くすため、この点を考慮した設計
が必要である。As shown in FIG. 2D, the medium water large diameter 2 area poison rod 28 has the same outer tube 2 as the solid large diameter 2 area poison rod 27.
8a, an inner pipe 28b, and a ring-shaped poisonous substance pellet 28c, but there is no core poisonous substance, and the reactor water is flown into the inner pipe 28b through the water passage hole 28d as shown by an arrow b to such an extent that it does not boil. They differ in points. When the inner diameter of the inner pipe 28b is increased, the reactivity effect as a poison rod increases, but the combustion is exhausted at an early stage. Therefore, a design considering this point is necessary.

【００４３】偏流短尺燃料棒２９は図２（Ｅ）に示すよ
うに、通常の燃料棒２２と同様に金属管２５にペレット
２４を充填した構成であるが、上端側の一定長さ範囲に
亘る部分を細径管３０としたものである。なお、細径管
３０には細径燃料物質の採用も可能であり、また管に代
えて中実な棒構造を採用してもよい。この細径管３０の
外周部に、偏流機構３１として、高速炉で用いられるワ
イヤスペーサと類似の螺旋状ワイヤ等からなる偏流部材
３１ａが巻装され、これにより細径管３０の外周面を流
れる冷却水が旋回流を起こすことになっている。この旋
回流により、チャンネルボックス２１の表面の冷却能力
の高い水を近隣の燃料棒２２の方へ振り向けることがで
きる。なお、偏流短尺燃料棒２９の本数が多過ぎると、
燃料のインベントリが減少したり反応度損失を生じた
り、出力ピーキングが過大になるなど、種々の問題が生
じ易いため、本数はやや少なめが良い。本実施例ではチ
ャンネルボックス２１に沿って８本設けられている。こ
のうち、バンドルコーナに位置する短尺燃料棒２９ａだ
け設け、中央側のもの２９ｂは通常の燃料棒に代えた方
が良い場合も考えられる。As shown in FIG. 2 (E), the drift short fuel rod 29 has a structure in which the metal pipe 25 is filled with the pellets 24 as in the case of the normal fuel rod 22, but it extends over a fixed length range on the upper end side. The portion is a small-diameter tube 30. It should be noted that a small-diameter fuel substance can be adopted for the small-diameter pipe 30, and a solid rod structure may be adopted instead of the pipe. As a non-uniform flow mechanism 31, a non-uniform flow member 31a made of a spiral wire or the like similar to a wire spacer used in a fast reactor is wound around the outer peripheral portion of the small-diameter pipe 30. The cooling water is supposed to create a swirling flow. This swirling flow allows water having a high cooling capacity on the surface of the channel box 21 to be directed toward the adjacent fuel rods 22. In addition, if the number of the non-uniform flow short fuel rods 29 is too large,
The number of fuels should be a little small, because various problems such as reduced fuel inventory, loss of reactivity, and excessive output peaking are likely to occur. In this embodiment, eight channels are provided along the channel box 21. Of these, it may be considered that it is better to provide only the short fuel rods 29a located at the bundle corners and replace the central one 29b with a normal fuel rod.

【００４４】図３は、図１の燃料集合体２０からチャン
ネルボックス２１を取り外した燃料バンドル２０ａを側
面視で模式的に示したものであり、合せて太径水棒２
６、太径２領域毒物棒２７，２８および偏流短尺燃料棒
２９を抽出して示している。符号ＬＴＰは下部タイプレ
ート３２、ＵＴＰは上部タイプレート３３、ＳＰ１〜Ｓ
Ｐ７は格子状のスペーサ３４をそれぞれ示している。FIG. 3 is a side view schematically showing the fuel bundle 20a with the channel box 21 removed from the fuel assembly 20 of FIG.
6, the thick two-region poison rods 27 and 28 and the drift short fuel rod 29 are extracted and shown. Code LTP is lower tie plate 32, UTP is upper tie plate 33, SP1-S
P7 indicates the lattice-shaped spacers 34, respectively.

【００４５】ＢＷＲ用燃料集合体では上端側のスペーサ
（ＳＰ６，ＳＰ７）付近で冷却水の冷却能力の余裕が小
さくなりやすいことが知られているため、本実施例で
は、太径水棒２６と太径２領域毒物棒２７，２８とを共
にこの付近から上側（下流側）で細径管３５としたもの
である。この細径管３５には、図４（Ａ）に示す短尺管
３６付き旋回羽根３７や、図４（Ｂ）に示す円錐形のフ
ロー制御材３８が装着され、近隣の燃料棒２２側に向け
て冷却水を矢印ｃの如く供給するようになっている。こ
こで短尺管３６にはスペーサ３４が当接または保持さ
れ、その直径は細径化されていない部分の直径と同一と
され、これにより細径化していない場合と同様にバンド
ルを組み立てたり解体することができ、従来の燃料組み
立て装置あるいは解体装置をそのまま使用できるように
なっている。短尺管３６の上下流側の端部３６ａ，３６
ｂには冷却水の不要な圧力損失を避けるため図４に示す
ように、テーパ付き断面としたり、流線形構造とするこ
とが望ましい。In the BWR fuel assembly, it is known that the margin of the cooling capacity of the cooling water tends to be small near the spacers (SP6, SP7) on the upper end side. The large diameter two-region poisoning rods 27 and 28 are both formed into a small diameter pipe 35 on the upper side (downstream side) from this vicinity. A swirl vane 37 with a short pipe 36 shown in FIG. 4 (A) and a conical flow control material 38 shown in FIG. 4 (B) are attached to the small-diameter pipe 35 and directed toward the adjacent fuel rod 22 side. Cooling water is supplied as indicated by arrow c. Here, the spacer 34 is brought into contact with or held by the short tube 36, and the diameter thereof is the same as the diameter of the non-thinned portion, so that the bundle is assembled or disassembled in the same manner as in the case where the diameter is not reduced. Therefore, the conventional fuel assembly apparatus or dismantling apparatus can be used as it is. The upstream and downstream ends 36a, 36 of the short pipe 36
In order to avoid unnecessary pressure loss of the cooling water, it is desirable that b has a tapered cross section or a streamline structure as shown in FIG.

【００４６】図４（Ｃ）は、同図（Ａ）の変形例を示し
ている。即ち、短尺管３６の上下流側端部が共に円錐状
の外形とされて滑らかに変化している。このように外形
が滑らかに変化しているので、冷却水は矢印ｄに示すよ
うに外周側に偏流し、近隣燃料棒に対する冷却効率が向
上する。FIG. 4C shows a modification of FIG. 4A. That is, both the upstream and downstream ends of the short pipe 36 have a conical outer shape and smoothly change. Since the outer shape changes smoothly in this way, the cooling water is unevenly flown to the outer peripheral side as shown by the arrow d, and the cooling efficiency for the neighboring fuel rods is improved.

【００４７】図４（Ｄ）は前述した偏流短尺燃料棒２９
の細径管３０部分を拡大して示している。同図に示すよ
うに、冷却水旋回機構としての偏流部材３１ａが取り付
けられている。この機構には他の変形例も考えられる。
たとえば棒状のものに緩やかなピッチで比較的深いネ
ジ、あるいは溝を形成してもよい。FIG. 4D shows the above-mentioned non-uniform flow short fuel rod 29.
The small-diameter tube 30 is shown in an enlarged manner. As shown in the figure, a drift member 31a as a cooling water swirl mechanism is attached. Other variations of this mechanism are possible.
For example, a relatively deep screw or groove may be formed at a moderate pitch on a rod-shaped object.

【００４８】なお、偏流短尺燃料棒２９のスペーサ当接
部には、図４（Ａ）に類似した短尺管（ただし、スペー
サ保持部材は取り付けない）が取り付けられている。ま
た、冷却水旋回機構によりチャンネルボックス２１の内
表面側を流れる冷却水が近隣の燃料棒２２へ供給され
る。A short pipe similar to that shown in FIG. 4A (however, the spacer holding member is not attached) is attached to the spacer contact portion of the non-uniform flow short fuel rod 29. Further, the cooling water swirling mechanism supplies the cooling water flowing on the inner surface side of the channel box 21 to the adjacent fuel rods 22.

【００４９】図５〜図９は本発明の燃料集合体２０を構
成する各種棒状物の長さ方向構造を模式的に、より詳細
に示したものである。即ち、図５は図２（Ｂ）に示した
太径水棒２６の全体図で、可燃性毒物としてのＧｄ筒２
６ｃが外管２６ａと内管２６ｂとからなる２重管の内部
に密封されている。また、図６は通常の長尺燃料棒２２
および従来型の毒物棒２３、図７は中実太径２領域毒物
棒２７、図８は中水太径２領域毒物棒２８、図９は偏流
短尺燃料棒２９をそれぞれ示している。これら図５〜図
９に示した各部材の構成については既に説明したので、
図２〜図４（ならびに図２６等）と同一部分に同一符号
を付して、その説明は省略する。FIGS. 5 to 9 are schematic and more detailed views showing the longitudinal structure of various rod-shaped objects which constitute the fuel assembly 20 of the present invention. That is, FIG. 5 is an overall view of the large diameter water rod 26 shown in FIG.
6c is sealed inside a double pipe composed of an outer pipe 26a and an inner pipe 26b. In addition, FIG. 6 shows an ordinary long fuel rod 22.
7 shows a solid large-diameter two-region poison rod 27, FIG. 8 shows a medium water large-diameter two-region poison rod 28, and FIG. 9 shows a drift short fuel rod 29. Since the configuration of each member shown in FIGS. 5 to 9 has already been described,
2 to 4 (and FIG. 26 and the like) are designated by the same reference numerals, and the description thereof will be omitted.

【００５０】以上で説明した第１の実施例の燃料集合体
２０によれば、中性子束が高い位置に太径２領域毒物棒
２７，２８を配置することにより、大きい中性子増倍率
抑制効果が得られるようになり、燃料に可燃性毒物を添
加した構成の毒物棒２３の本数が削減可能となる。この
結果、燃料集合体２０内の出力ピーキングの緩和が図れ
るとともに、プルトニウムをより多く装荷でき、また太
径水棒２６の周りに集まりがちな冷却水の流れが調整さ
れ、燃料棒２２の冷却に効果的に活用されるため、燃料
の冷却特性が向上するようになる。According to the fuel assembly 20 of the first embodiment described above, a large neutron multiplication factor suppressing effect can be obtained by disposing the thick diameter 2 region poison rods 27 and 28 at the position where the neutron flux is high. As a result, it is possible to reduce the number of poison rods 23 having a structure in which a combustible poison is added to the fuel. As a result, the output peaking in the fuel assembly 20 can be mitigated, more plutonium can be loaded, and the flow of cooling water that tends to collect around the large diameter water rod 26 is adjusted to cool the fuel rod 22. Since it is effectively used, the cooling characteristics of the fuel are improved.

【００５１】また、熱中性子束が高くなる位置が太径と
なっている太径水棒２６の管肉部にＧｄ筒１６ｃなどの
可燃性毒物を含ませているので、燃料集合体２０の中性
子増倍率抑制効果が大きくなる。さらに、太径水棒２６
の外周部および内周部の水に面する表面積が従来の毒物
棒の表面積に比べて著しく大きいため、１本の毒物入り
太径水棒２６の中性子増倍率抑制効果は、従来の毒物棒
の数倍（例えば５倍）に及ぶ。したがって、その分だけ
通常の毒物棒２３の本数を低減することができ、代りに
通常の燃料棒２２を使用することができる。原子炉運転
サイクルのうちで太径多領域毒物棒の中性子吸収作用が
続いている期間は太径水棒の中性子吸収作用は抑制され
るため、その期間における中性子増倍率の過大な抑制効
果は大幅に緩和される。Further, since the thick water rod 26 having a large position where the thermal neutron flux becomes high contains the combustible poisonous substance such as the Gd cylinder 16c in the tube portion of the large diameter water rod 26, the neutron of the fuel assembly 20 is The effect of suppressing the multiplication factor becomes large. Furthermore, a large diameter water rod 26
Since the surface area of the outer peripheral portion and the inner peripheral portion facing the water is significantly larger than the surface area of the conventional poison rod, the neutron multiplication suppressing effect of one large diameter water rod 26 containing a poison is equal to that of the conventional poison rod. Several times (for example, five times). Therefore, the number of normal poison rods 23 can be reduced by that amount, and the normal fuel rods 22 can be used instead. During the period in which the neutron absorption action of the large diameter multi-zone poison rod continues in the reactor operation cycle, the neutron absorption action of the large diameter water rod is suppressed, so the excessive suppression effect of the neutron multiplication factor during that period is significant. Is alleviated.

【００５２】そして、太径２領域毒物棒２７の中性子吸
収作用が弱まった頃に毒物入り太径水棒２６の中性子吸
収作用が発揮される。運転サイクルの終了時点の少し前
では一般に毒物作用は最小とされるが、その際は単に太
径水棒２６として作用し、燃料集合体２０のサイクル末
期において不足がちとなる中性子増倍効果を向上させる
ことができる。なお、設計条件によってはサイクル末期
でも毒物作用を残す事も可能である。When the neutron absorbing action of the thick diameter two-region poison rod 27 is weakened, the neutron absorbing action of the poison-containing large diameter water rod 26 is exerted. Shortly before the end of the operation cycle, the poisoning action is generally minimized, but in that case, it acts simply as the large diameter water rod 26, and improves the neutron multiplication effect that tends to be insufficient at the end of the cycle of the fuel assembly 20. Can be made. Depending on the design conditions, it is possible to leave the toxic effect even at the end of the cycle.

【００５３】また、太径２領域毒物棒２８の内部に冷却
材、すなわち炉水を導入することで高速中性子が減速さ
れて毒物に吸収されやすい熱中性子となるため、燃料集
合体２０の中性子増倍率抑制効果が一段と増大される。Further, when a coolant, that is, reactor water is introduced into the large diameter two-region poison rod 28, the fast neutrons are decelerated to become thermal neutrons that are easily absorbed by the poisons, so that the neutron increase of the fuel assembly 20 is increased. The magnification suppression effect is further increased.

【００５４】しかも、太径２領域毒物棒２７の内部の可
燃性毒物２７ｄの濃度を外周部のそれより高くすると、
まず運転サイクルの初期の燃料集合体２０の中性子増倍
率が特に高くなりがちな期間において増倍率抑制作用を
済ませた後、外周部の可燃性毒物２７ｃの中性子吸収作
用が消滅し、内部の可燃性毒物２７ｄが緩やかに増倍率
抑制作用を発揮することになる。すなわち、本構成は燃
料集合体２０の中性子増倍率の実効的な値をほぼ一定に
保つ作用がある。Moreover, if the concentration of the burnable poison 27d inside the large diameter two-region poison rod 27 is made higher than that at the outer peripheral portion,
First, after the effect of suppressing the multiplication factor is completed in the period in which the neutron multiplication factor of the fuel assembly 20 tends to be particularly high in the early part of the operation cycle, the neutron absorbing action of the burnable poison 27c in the outer peripheral portion disappears, and the internal flammability is increased. The poison 27d gently exerts the multiplication factor suppressing effect. That is, this configuration has an effect of keeping the effective value of the neutron multiplication factor of the fuel assembly 20 substantially constant.

【００５５】さらに、本実施例によれば、細径化された
部分に装着された冷却水偏流機構３１の作用によって、
太径水棒２６および太径多領域毒物棒近傍に集まりがち
な冷却水を周辺の燃料棒２２の方へ偏流するため、燃料
の冷却効果が向上する。Further, according to the present embodiment, by the action of the cooling water distribution mechanism 31 attached to the narrowed portion,
The cooling water, which tends to gather near the large-diameter water rod 26 and the large-diameter multi-region poisoning rod, flows unevenly toward the peripheral fuel rods 22, so that the fuel cooling effect is improved.

【００５６】さらにまた、チャンネルボックス２１に面
した一部の燃料棒２２あるいは毒物棒２３のうち、冷却
水の流れの下流側で燃料棒２２の熱的余裕の少ない部分
を細径化し、そこに冷却水偏流機構３１を設けることに
より、その冷却水偏流作用によって構造材内面の冷却水
が隣接燃料棒２２の方へ偏流され、隣接燃料棒２２の冷
却に寄与することができる。Further, of the part of the fuel rods 22 or poison rods 23 facing the channel box 21, the portion of the fuel rods 22 having a small thermal margin is made thin at the downstream side of the flow of the cooling water, and the diameter is reduced there. By providing the cooling water non-uniform flow mechanism 31, the cooling water on the inner surface of the structural member is non-uniformly flowed toward the adjacent fuel rods 22 due to the cooling water non-uniform flow action, which can contribute to the cooling of the adjacent fuel rods 22.

【００５７】また、太径２領域毒物棒２７，２８、燃料
棒２２、毒物棒２３または太径水棒２６の下流側の細径
化されスペーサと係合する部分に、上流側で細径化して
いない部分とほぼ同じ直径の短尺管３６が装着されてい
るため、スペーサ３４自体も特に変更する必要がなく、
また燃料集合体２０の組み立てや必要時の解体作業の場
合でも、従来とほぼ同様に作業を行うことができる。Further, the diameter of the large diameter two-region poison rods 27, 28, the fuel rod 22, the poison rod 23, or the thick water rod 26, which is reduced in diameter on the downstream side and engages with the spacer, is reduced on the upstream side. Since the short tube 36 having substantially the same diameter as that of the unattached portion is attached, it is not necessary to change the spacer 34 itself,
Further, even in the case of assembling the fuel assembly 20 and the disassembling work when necessary, the work can be performed almost in the same manner as the conventional one.

【００５８】なお、短尺管３６の上流側と下流側とにテ
ーパ部３６ａ，３６ｂを形成することにより、冷却特性
の改良を行うことができる。即ち、細径管３５と短尺管
３６との間を円錐状に外径が滑らかにつながるようにテ
ーパ部３６ａ，３６ｂを設けることにより、スペーサ部
での流路面積変化が滑らかとなり、流れに対する外乱を
抑制することができる。また、テーパ部３６ａ，３６ｂ
により冷却水が近隣の長尺燃料棒に振り向けられるの
で、長尺燃料棒２２の冷却効率が改善される。By forming the tapered portions 36a and 36b on the upstream side and the downstream side of the short pipe 36, the cooling characteristic can be improved. That is, by providing the tapered portions 36a and 36b so that the outer diameter is smoothly connected in a conical shape between the small diameter pipe 35 and the short length pipe 36, the flow passage area change in the spacer portion becomes smooth, and the disturbance to the flow is disturbed. Can be suppressed. In addition, the tapered portions 36a and 36b
As a result, the cooling water is directed to the adjacent long fuel rods, so that the cooling efficiency of the long fuel rods 22 is improved.

【００５９】なお、以上に説明した第１の実施例におい
ては、下記のように種々の変形が可能である。The first embodiment described above can be modified in various ways as described below.

【００６０】（１）太径水棒を１重管とし、可燃性毒物
を除く。 （２）太径２領域毒物棒を全て中実または中水毒物棒と
する。 （３）太径２領域毒物棒の一部または全部を３領域以上
とする。 （４）太径２領域毒物棒の中に充填されているペレット
等の表面にジルコニウムボライド（ＺｒＢ2 ）等の可燃
性毒物を塗布する。 （５）中実太径２領域毒物棒の内管内に、または内管を
用いないで内部に、硼素化合物、希土類元素の酸化物等
を充填する。 （６）下流側で水棒、毒物棒、偏流短尺燃料棒などの細
径化する範囲をいろいろ変化させる。 （７）偏流短尺燃料棒の位置、本数、あるいは細径化す
る範囲等をいろいろ変え、さらにそれらを適宜組み合わ
せる。 （８）中実可燃性毒物棒の位置、濃度、本数等を変更す
る。(1) Use a large-diameter water rod as a single tube and remove combustible poisons. (2) All the large diameter two-region poison sticks are solid or solid water poison sticks. (3) Two or more large diameter poisonous rods are partially or entirely made into three or more regions. (4) A combustible poison such as zirconium boride (ZrB 2 ) is applied to the surface of pellets or the like filled in the thick two-region poison rod. (5) A boron compound, an oxide of a rare earth element, or the like is filled in the inner tube of the solid large-diameter two-region poison bar, or without using the inner tube. (6) On the downstream side, the range of reducing the diameter of water rods, poison rods, short-distance drift fuel rods, etc. is variously changed. (7) The position, the number, or the range of narrowing of the non-uniformly distributed short fuel rods are variously changed, and further these are appropriately combined. (8) Change the position, concentration, number, etc. of solid burnable poisonous rods.

【００６１】図１０は本発明の第２の実施例を示してい
る。本実施例は、全ての燃料棒２２が比較的広い冷却水
の流れる間隙に面するように燃料棒２２の配列を変更し
たものである。FIG. 10 shows a second embodiment of the present invention. In this embodiment, the arrangement of the fuel rods 22 is changed so that all the fuel rods 22 face a relatively wide gap in which the cooling water flows.

【００６２】即ち、この燃料集合体２０では、太径水棒
２６の回りに、４本の中水太径２領域毒物棒２８と、符
号Ｇで示した４本のＧ毒物棒２３とが配置されている。
Ｇ毒物棒２３内でのＵＯ2 へのＧｄ2 Ｏ3 添加濃度を比
較的高くし（例えば８〜１０重量％）、毒物入り太径水
棒２６および中水太径２領域毒物棒２８の核的特性から
くるサイクル末期での燃料集合体の過度の反応度上昇問
題を避けている。That is, in this fuel assembly 20, four medium-water large-diameter two-region poison rods 28 and four G poison rods 23 indicated by the symbol G are arranged around the large-diameter water rod 26. Has been done.
The concentration of Gd 2 O 3 added to UO 2 in the G poison rod 23 is made relatively high (for example, 8 to 10% by weight), and the core of the large diameter water rod 26 containing poison and the large diameter medium water 2 region poison rod 28 is added. The excessive reactivity increase problem of the fuel assembly at the end of the cycle, which is caused by the physical characteristics, is avoided.

【００６３】このような本実施例の構成によれば、冷却
特性が良く、かつ中性子の共鳴吸収を逃れる確率が増大
し、出力運転中の反応度利得がある。チャンネルコーナ
の燃料棒２２には偏流短尺燃料棒２９を採用して冷却特
性の低下が防止でき、停止余裕も良くなる。また、燃料
集合体２０を構成する燃料濃縮度の種類を低減できる場
合も生じる。According to the structure of the present embodiment as described above, the cooling characteristic is good, the probability of escaping the resonance absorption of neutrons is increased, and there is the reactivity gain during the output operation. A short-flow drift fuel rod 29 is adopted as the fuel rod 22 of the channel corner to prevent the cooling characteristic from deteriorating and the stop margin to be improved. Further, there may be a case where the type of fuel enrichment that constitutes the fuel assembly 20 can be reduced.

【００６４】図１１は本発明の第３の実施例を示してい
る。本実施例は第２の実施例と類似しているが、燃料の
濃縮度が比較的低い場合に適しているもので、毒物入り
太径水棒２６の周りにＧ毒物棒が配置されておらず、通
常の燃料棒２２が４５度の対角線に対して対称に配置さ
れている。このような構成によると、中水太径２領域毒
物棒２８のＧｄ2 Ｏ3 濃度は比較的低く抑えられている
（例えば２〜４重量％）ものと、高いもの（例えば５〜
８重量％）との組み合わせとすることによって、サイク
ル末期における燃料集合体の過度の反応度上昇問題を緩
和することができる。FIG. 11 shows a third embodiment of the present invention. This embodiment is similar to the second embodiment, but is suitable for the case where the concentration of fuel is relatively low, and the G poison rod is arranged around the large diameter water rod 26 containing poison. Instead, the normal fuel rods 22 are arranged symmetrically with respect to the 45-degree diagonal. With such a configuration, the Gd 2 O 3 concentration of the medium-water large-diameter two-region poison rod 28 is relatively low (for example, 2 to 4% by weight) and high (for example, 5 to 5%).
8% by weight) can alleviate the excessive reactivity increase problem of the fuel assembly at the end of the cycle.

【００６５】図１２は本発明の第４の実施例を示してい
る。本実施例は前記各実施例と異なり、２本の毒物入り
太径水棒２６が燃料集合体２０の中央部に隣接配置さ
れ、両者と直交するように隣接して２本の中水太径２領
域毒物棒２８が配置されている。FIG. 12 shows a fourth embodiment of the present invention. In this embodiment, unlike the above-described embodiments, two large water rods 26 containing poisonous substances are arranged adjacent to each other in the central portion of the fuel assembly 20, and two large diameters of medium water are adjacent to each other so as to be orthogonal to each other. A two-zone poison stick 28 is arranged.

【００６６】もし、この位置に普通の直径の燃料棒や従
来型の毒物棒を配置したとすると、その周りの冷却水流
路が広いため、冷却水が集り易く、従って冷却特性が低
下するが、本実施例によれば、その弊害が解除される。
本実施例では水棒は断面を円形としているがそれに限定
する必要がないのは、他の実施例も含めて同様である。If a fuel rod having a normal diameter or a conventional poison rod is arranged at this position, the cooling water flow passage around the fuel rod is wide, so that the cooling water is likely to collect and the cooling characteristics are deteriorated. According to this embodiment, the adverse effect is eliminated.
In this embodiment, the water rod has a circular cross section, but it is not limited to this, as is the case with other embodiments.

【００６７】図１３は本発明の第５の実施例を示してい
る。本実施例では２本の隣接する毒物入り太径水棒２６
と直交して２本の中実太径２領域毒物棒（内部で濃度が
高く、外周部で低い）２７が配置されている。低濃縮度
用燃料集合体であるため、図１２の場合８本のＧ毒物棒
が用いられているのに対し、図１３の例では４本となっ
ている。FIG. 13 shows a fifth embodiment of the present invention. In this embodiment, two adjacent large-diameter water rods 26 containing poisons
Two solid large-diameter two-region poison sticks (concentration is high inside and low at the outer periphery) 27 are arranged orthogonally to. Since it is a low enrichment fuel assembly, eight G poison rods are used in the case of FIG. 12, whereas four G poison rods are used in the example of FIG.

【００６８】本実施例の構成は燃料の濃縮度が比較的低
い場合に適している。The configuration of this embodiment is suitable when the fuel enrichment is relatively low.

【００６９】図１４は本発明の第６の実施例を示してい
る。本実施例は第４の実施例と類似しているが、従来型
のＧ毒物棒２３が偏流短尺燃料棒２９に接近した配置と
され、また、中水太径に代えて中実太径２領域毒物棒２
７（但し、外周部にはガドリニア毒物が含まれていない
もの）が用いられている。FIG. 14 shows a sixth embodiment of the present invention. This embodiment is similar to the fourth embodiment, except that the conventional G poison rod 23 is disposed close to the drift short fuel rod 29, and the solid large diameter 2 is used instead of the medium water large diameter. Area poison stick 2
7 (however, gadolinia poison is not contained in the outer peripheral portion) is used.

【００７０】本実施例によれば、図１０に示した場合に
比べて、反応度抑制効果は若干小さいものの、燃焼サイ
クルに亘る中性子増倍特性の変化を小さくし易い効果が
ある。According to this embodiment, although the reactivity suppressing effect is slightly smaller than that shown in FIG. 10, the change in the neutron multiplication characteristics over the combustion cycle can be easily reduced.

【００７１】図１５は本発明の第７の実施例を示してい
る。本実施例は、前記第６の実施例と構造的にほぼ同様
であるが、２本の太径水棒のうち一方２６はガドリニウ
ムを含み、他方２６′は硼素化合物を含んでいる。FIG. 15 shows a seventh embodiment of the present invention. This embodiment is structurally similar to the sixth embodiment, but one of the two large diameter water rods 26 contains gadolinium and the other 26 'contains a boron compound.

【００７２】本実施例によれば、硼素の中性子吸収断面
積がＧｄのそれより小さいため、燃焼速度が遅く、その
ためサイクル末期における中性子増倍率の過度の増加を
抑制することができる。硼素化合物の使用方法として
は、Ａｌ2 Ｏ3 −Ｂ4 Ｃ混合焼結体を外管２６ａと内管
２６ｂとの間に挿入したり、外管２６ａの内面及び／又
は内管２６ｂの外面にＺｒＢ2 を塗布するなどの手段が
可能である。According to the present embodiment, since the neutron absorption cross section of boron is smaller than that of Gd, the burning rate is slow, and therefore the excessive increase of the neutron multiplication factor at the end of the cycle can be suppressed. The boron compound may be used by inserting an Al 2 O 3 —B 4 C mixed sintered body between the outer tube 26a and the inner tube 26b, or by inserting it on the inner surface of the outer tube 26a and / or the outer surface of the inner tube 26b. Means such as applying ZrB 2 are possible.

【００７３】図１６は本発明の第８の実施例を示してい
る。本実施例は前記第５の実施例と類似しているが、燃
料集合体２０が内部の２本の毒物入り太径水棒２６と２
本の太径２領域毒物棒２７（内部にＧｄを含むペレット
があり、外周部の燃料ペレットにはＺｒＢ2 のコーティ
ングが施されている）とを取り巻くように燃料棒を３×
３を一グループとする水ギャップで離間された８個のサ
ブハンドルで取り巻かれて構成されている。FIG. 16 shows an eighth embodiment of the present invention. This embodiment is similar to the fifth embodiment, but the fuel assembly 20 has two poisonous large diameter water rods 26 and 2 inside.
3 x fuel rods surrounding a large-diameter two-region poison rod 27 (there are pellets containing Gd inside and the fuel pellets on the outer periphery are coated with ZrB 2 )
It is composed of eight sub-handles separated by a water gap in groups of three.

【００７４】本実施例によれば、前記第５の実施例より
も共鳴を逃れる確率が高くなるため、中性子増倍率を若
干大きくすることができる。また、コーナから３番目の
燃料棒２２は、第５実施例ではチャンネルボックス２１
に面しているのに対し、本実施例では広い水ギャップに
面しているため冷却特性も改良される。According to this embodiment, the probability of escape from resonance is higher than that in the fifth embodiment, so that the neutron multiplication factor can be slightly increased. Further, the third fuel rod 22 from the corner is the channel box 21 in the fifth embodiment.
On the other hand, in the present embodiment, the cooling characteristic is also improved because it faces a wide water gap.

【００７５】図１７は本発明の第９の実施例を示してい
る。本実施例も、前記第５の実施例と類似しているが、
燃料棒２２の配置が一様でなく、図１０および図１１の
場合とほぼ同様に多くの水ギャップを有する離間配置と
なっている。本実施例によれば、冷却特性が良く、かつ
図１３の場合よりも中性子増倍率の若干高い燃料集合体
が得られ、燃焼度向上に有利である。FIG. 17 shows a ninth embodiment of the present invention. This embodiment is also similar to the fifth embodiment, except that
The arrangement of the fuel rods 22 is not uniform, and the fuel rods 22 are spaced apart from each other and have many water gaps as in the cases of FIGS. 10 and 11. According to this example, a fuel assembly having good cooling characteristics and a slightly higher neutron multiplication factor than in the case of FIG. 13 is obtained, which is advantageous for improving the burnup.

【００７６】図１８は本発明の第１０の実施例を示して
いる。本実施例では、燃料集合体２０内の燃料棒２２が
一様には配列されておらず、４−１−４型の粗密構造に
配列されている。中央部には２本の毒物入り太径水棒２
６が隣接配置され、それらを挾むように６本の太径２領
域毒物棒２７，２８が配置されている。これら６本の毒
物棒のうち３本組の中央のもの２８は中水２領域太径毒
物棒、両側のもの２７は中実２領域太径毒物棒とされて
いる。中実のものは、外周部に低濃度のガドリニアが添
加されている。チャンネルボックス２１に面する燃料棒
２２のうち、一つ置きの８本のものは短尺化されてお
り、チャンネルボックス２１の内面から冷却余裕の大き
い冷却水が近接燃料棒へ供給される。FIG. 18 shows a tenth embodiment of the present invention. In this embodiment, the fuel rods 22 in the fuel assembly 20 are not uniformly arranged, but are arranged in a 4-1-4 type coarse and dense structure. 2 large diameter water rods with 2 poisons in the center
6 are arranged adjacent to each other, and six large-diameter two-region poison rods 27 and 28 are arranged so as to sandwich them. Of these 6 poison rods, the central one 28 of the three sets is a medium water 2 area thick poison rod, and the ones on both sides 27 are solid 2 area thick poison rods. The solid one has a low concentration of gadolinia added to the outer periphery. Of the fuel rods 22 facing the channel box 21, every other eight fuel rods 22 are shortened, and cooling water with a large cooling margin is supplied from the inner surface of the channel box 21 to the adjacent fuel rods.

【００７７】本実施例によれば、可燃性毒物による燃料
集合体２０の中性子増倍率抑制効果が大きく、しかも長
続きする。したがって濃縮度の比較的高い燃料集合体に
適している。また、燃料棒２２が粗密に配置されている
ため、前述のように運転中の反応度を高めるのに有利で
ある。According to this embodiment, the effect of suppressing the neutron multiplication factor of the fuel assembly 20 by the burnable poison is large and lasts long. Therefore, it is suitable for a fuel assembly having a relatively high enrichment. Further, since the fuel rods 22 are densely arranged, it is advantageous to increase the reactivity during operation as described above.

【００７８】図１９は本発明の第１１の実施例を示して
いる。本実施例は図１０に示した実施例と類似している
が、燃料棒２２は９×９ではなく１０×１０に配列され
ている。FIG. 19 shows an eleventh embodiment of the present invention. This embodiment is similar to the embodiment shown in FIG. 10, but the fuel rods 22 are arranged in 10 × 10 instead of 9 × 9.

【００７９】本実施例によれば作用効果は図１０の場合
と略同様である。但し、チャンネルボックスに面してい
る燃料棒２２は２本おきに短尺化されており、冷却特性
がさらに改良されている。According to this embodiment, the operation and effect are substantially the same as those in the case of FIG. However, every two fuel rods 22 facing the channel box are shortened so that the cooling characteristics are further improved.

【００８０】図２０は本発明の第１２の実施例を示して
いる。本実施例では、燃料棒２２が１１×１１に配置さ
れており、中央に１本の毒物入り太径水棒２６が配置さ
れ、その周りを取り巻くように８本の中実太径２領域毒
物棒２７が配置されている。燃料集合体内の燃料棒本数
は、初期のＢＷＲでは６×６であったが、７×７、８×
８、９×９という具合に大きくなって来ており、さらに
１０×１０、１１×１１へとさらに大きくなるものと想
定される。本実施例はそれに対応したものである。FIG. 20 shows a twelfth embodiment of the present invention. In this embodiment, the fuel rods 22 are arranged in 11 × 11, one large diameter water rod 26 containing poison is arranged in the center, and eight solid large diameter two-region poisons surrounding the same are arranged. A bar 27 is arranged. The number of fuel rods in the fuel assembly was 6 × 6 in the initial BWR, but 7 × 7, 8 ×
It has been increasing to 8 × 9 × 9, and is expected to further increase to 10 × 10 and 11 × 11. This embodiment corresponds to that.

【００８１】図２１は本発明の第１３の実施例を示して
いる。本実施例のタイプの燃料集合体２０は基本的には
ヨーロッパで開発されたもので、燃料集合体２０の燃料
バンドル２０ａは４個のサブバンドル２０′ａに分割さ
れており、それぞれの間にスリット状の非沸騰水領域４
０が設けられている。FIG. 21 shows a thirteenth embodiment of the present invention. The fuel assembly 20 of the type of this embodiment is basically developed in Europe, and the fuel bundle 20a of the fuel assembly 20 is divided into four sub-bundles 20'a, and in between. Slit-shaped non-boiling water area 4
0 is provided.

【００８２】この例では中央に毒物入り太径水棒２６が
配置されている。スリット部の構造材はチャンネルボッ
クスのそれと同じく、ジルカロイで構成されている。ス
リット状非沸騰水領域４０には必要に応じて可燃性毒物
を添加した中性子吸収板を挿入することも可能である。
また、中央の水棒を取り囲むようにして、４本の太径２
領域毒物棒２７，２８が配置されている。そのうち２本
２８が中水太径２領域毒物棒、他の２本２７は中実太径
２領域毒物棒とされている。燃料集合体２０の各コーナ
部の燃料棒２２は冷却特性が一般に良くないため、偏流
短尺燃料棒２９が配置されている。In this example, a large diameter water rod 26 containing a poison is arranged in the center. The structural material of the slit part is made of Zircaloy, like the channel box. It is also possible to insert a neutron absorbing plate added with a burnable poison in the slit-shaped non-boiling water region 40, if necessary.
In addition, 4 large diameter 2
Area poison sticks 27, 28 are arranged. Two of them 28 are medium-water large-diameter two-region poison rods, and the other two 27 are solid large-diameter two-region poison rods. Since the cooling characteristics of the fuel rods 22 at the respective corners of the fuel assembly 20 are generally poor, the drift short fuel rods 29 are arranged.

【００８３】なお、以上の実施例においては、ＢＷＲ用
燃料集合体の場合につき、多数の例を挙げて説明した
が、本発明はＢＷＲ燃料集合体の場合に限定されない。
加圧水型原子炉（ＰＷＲ）やイギリスや日本で開発され
た沸騰軽水冷却・重水減速型熱中性子炉（ＳＧＨＷＲ，
ＡＴＲ）などでも利用できる。In the above embodiments, the case of the BWR fuel assembly has been described by giving many examples, but the present invention is not limited to the case of the BWR fuel assembly.
Pressurized water reactor (PWR) and boiling light water cooling / heavy water moderator thermal neutron reactor (SGHWR, developed in the United Kingdom and Japan
ATR) etc. can also be used.

【００８４】以下、ＰＷＲ用燃料集合体、及びＡＴＲ、
ＣＡＮＤＵ、ＳＧＨＷＲ等の圧力管型原子炉用燃料集合
体の場合について簡単に説明する。Hereinafter, the fuel assembly for PWR and the ATR,
A case of a fuel assembly for a pressure tube type reactor such as CANDU and SGHWR will be briefly described.

【００８５】図２２は本発明の第１４の実施例として、
ＰＷＲ用燃料集合体を示している。燃料棒２２は１５×
１５に配置され、５本の毒物入り太径水棒２６が対称に
配置されている。中央の水棒は構造的条件から他の４本
より細径となっており、その周りに４本の中実太径２領
域毒物棒２７が配置されている。この毒物棒のガドリニ
ア濃度は内部で高く、外周部で低くなっている。ＰＷＲ
燃料集合体の周りにはチャンネルボックスは配置されて
いないため、偏流短尺燃料棒は配置されていない。FIG. 22 shows a fourteenth embodiment of the present invention.
1 illustrates a PWR fuel assembly. 15 × fuel rod 22
15 large water rods 26 containing poisonous substances are arranged symmetrically. The central water rod has a smaller diameter than the other four due to structural conditions, and four solid large-diameter two-region poison rods 27 are arranged around the water rod. The gadolinia concentration of this poison stick is high inside and low at the outer periphery. PWR
Since the channel box is not arranged around the fuel assembly, the non-uniform flow short fuel rods are not arranged.

【００８６】本実施例においても、ＢＷＲ用燃料集合体
と同様の効果が奏される。Also in this embodiment, the same effect as that of the BWR fuel assembly is obtained.

【００８７】図２３〜図２５は本発明の第１５の実施例
として、３種の圧力管型原子炉用燃料集合体２０を示し
ている。本実施例では各燃料棒２２がほぼ等間隔で外形
が円形となるように同心円状に配置されて燃料バンドル
（燃料クラスターと呼ばれることが多い）となってい
る。燃料バンドルは円形の圧力管４１内に配置されて燃
料集合体２０となっている。実際には、圧力管４１の周
りに図示しない気体の断熱層があり、さらにその周りを
カランドリア管が取り巻いている。圧力管４１の内面に
面して配列された燃料棒２２のうち５本ごとに偏流短尺
燃料棒２９が配置され、圧力管４１の内面付近の冷却余
裕のある水を近隣の燃料棒２２へ振り掛ける構成とされ
ている。燃料集合体２０の中央部分には、毒物入り太径
水棒２６とそれを取り巻くように太径２領域毒物棒２
７，２８が配置されている。23 to 25 show three kinds of fuel assemblies 20 for a pressure tube type reactor as a fifteenth embodiment of the present invention. In this embodiment, the fuel rods 22 are concentrically arranged so as to have a circular outer shape at substantially equal intervals to form a fuel bundle (often called a fuel cluster). The fuel bundle is arranged in the circular pressure pipe 41 to form the fuel assembly 20. In reality, there is a gas heat insulating layer (not shown) around the pressure pipe 41, and a calandria pipe surrounds the heat insulating layer. Unevenly distributed short fuel rods 29 are arranged for every five fuel rods 22 arranged so as to face the inner surface of the pressure pipe 41, and water having a cooling margin near the inner face of the pressure pipe 41 is sprinkled on the adjacent fuel rods 22. It is configured to. At the center of the fuel assembly 20, a large diameter water rod 26 containing poison and a large diameter 2 area poison rod 2 surrounding the water rod 26 are arranged.
7, 28 are arranged.

【００８８】図２３の例では中実太径２領域毒物棒２７
が４本、図２４および図２５の例では燃料濃縮度が高い
場合に必要であり、６本のうち３本が中実太径２領域毒
物棒２７、他の３本が中水太径２領域毒物棒２８とされ
ている。図２５の例では従来型のＧで示す毒物棒２３が
配置されており、燃料濃縮度が図２４の場合よりもさら
に高い場合に好適である。In the example of FIG. 23, a solid large diameter two area poison stick 27 is used.
24, and in the example of FIGS. 24 and 25, it is necessary when the fuel enrichment is high, and 3 out of 6 are solid large diameter 2 area poison rod 27 and the other 3 are medium water large diameter 2 It is designated as area poison stick 28. In the example of FIG. 25, the poisonous rod 23 shown by G of the conventional type is arranged, which is suitable when the fuel enrichment is higher than that of FIG.

【００８９】本発明の概念は以上に示したＢＷＲ、ＰＷ
Ｒ、あるいはイギリス、カナダ、日本などで開発された
圧力管型重水炉の燃料集合体のみに限らず、研究開発が
進められている高転換型軽水炉の燃料集合体にも適用す
ることができる。The concept of the present invention is based on the above-mentioned BWR and PW.
The present invention can be applied not only to the fuel assembly of the pressure tube type heavy water reactor developed in R, UK, Canada, Japan, etc., but also to the fuel assembly of the high conversion type light water reactor which is being researched and developed.

【００９０】[0090]

【発明の効果】以上で詳述したように、本発明に係る燃
料集合体によれば、太径多領域毒物棒が中性子束の高い
位置に配置され、かつ太径水棒にも必要に応じて可燃性
中性子毒物が添加されているため、燃料集合体の中性子
増倍率抑制効果を従来より大幅に増大することができ
る。その結果、従来から用いられてきた毒物棒、即ち核
燃料物質にガドリニア等の可燃性毒物を添加した燃料棒
の本数を低減することができる。従来の同種の毒物棒は
熱伝導率の低下抑制の必要から、高い濃度で添加するこ
とが困難であり、将来の高燃焼度化に向けた燃料集合体
の設計の難点とされており、毒物棒の本数が増大すると
出力分布の平坦化設計が困難となり、またプルトニウム
を用いる燃料集合体では、製造の複雑化とコスト上昇、
中性子増倍率抑制効果の低下などの理由からプルトニウ
ム燃料棒の中に可燃性毒物を添加することは極めて不利
であったが、この様な難点が、上述した本発明の構成に
より大幅に緩和され、従来型の毒物棒を必要最小限に低
減できる。As described above in detail, according to the fuel assembly of the present invention, the large-diameter multi-region poison rod is arranged at a position where the neutron flux is high, and the large-diameter water rod is also required as necessary. Since a combustible neutron poison is added to the fuel assembly, the effect of suppressing the neutron multiplication factor of the fuel assembly can be significantly increased compared to the conventional case. As a result, the number of conventionally used poison rods, that is, the number of fuel rods obtained by adding a burnable poison such as gadolinia to a nuclear fuel substance can be reduced. Conventional poison rods of the same kind are difficult to add at high concentrations because it is necessary to suppress the decrease in thermal conductivity, and it is considered to be a difficulty in designing fuel assemblies for higher burnup in the future. When the number of rods increases, it becomes difficult to design a flat power distribution, and in the fuel assembly using plutonium, manufacturing complexity and cost increase,
It was extremely disadvantageous to add a burnable poison to the plutonium fuel rod for reasons such as a decrease in the neutron multiplication factor suppression effect, but such a drawback is greatly alleviated by the above-described configuration of the present invention. The number of conventional poison sticks can be reduced to the minimum necessary.

【００９１】また、太径多領域毒物棒は太径水棒側面で
冷却水が集まり易い場所に配置されるため、このような
無駄な冷却水の集中が排除され、燃料棒の冷却特性が向
上できる。Further, since the large-diameter multi-zone poison rod is arranged at the side of the large-diameter water rod where cooling water is likely to collect, such wasteful concentration of cooling water is eliminated and the cooling characteristics of the fuel rod are improved. it can.

【００９２】さらに、チャンネルボックスの燃料バンド
ルを取り囲む構造材に面した冷却余裕の高い冷却水を、
偏流機構を有する偏流短尺燃料棒の作用により近隣の燃
料棒の冷却のために用いることができるため、燃料棒の
冷却特性の向上が図れる。その他、組立や解体の作業も
比較的容易に行える等の効果も奏される。Furthermore, the cooling water having a high cooling margin facing the structural material surrounding the fuel bundle of the channel box,
Since it can be used for cooling the neighboring fuel rods by the action of the short-flowing fuel rods having the non-uniform flow mechanism, the cooling characteristics of the fuel rods can be improved. In addition, the effect of relatively easy assembly and dismantling work can be achieved.

【図面の簡単な説明】[Brief description of drawings]

【図１】本発明に係る燃料集合体の第１の実施例を示す
もので、ＢＷＲ用燃料集合体の横断面図。FIG. 1 shows a first embodiment of a fuel assembly according to the present invention and is a cross-sectional view of a BWR fuel assembly.

【図２】図１における部品の拡大図で、（Ａ）は通常の
燃料棒及び毒物棒、（Ｂ）は毒物入り太径水棒、（Ｃ）
は中実太径２領域毒物棒、（Ｄ）は中水太径２領域毒物
棒、（Ｅ）は冷却水偏流機構を装着した偏流短尺燃料棒
をそれぞれ示す要部縦断面図。2 is an enlarged view of the parts in FIG. 1, (A) is a normal fuel rod and poison rod, (B) is a large water rod containing poison, (C)
Is a solid large-diameter two-zone poison rod, (D) is a medium-water large-diameter two-zone poison rod, and (E) is a longitudinal cross-sectional view of an essential portion showing a drift short fuel rod equipped with a cooling water drift mechanism.

【図３】前記実施例における燃料集合体からチャンネル
ボックスを取り外した状態の縦側面図で太径水棒および
太径多領域毒物棒ならびに偏流短尺燃料棒の軸方向高さ
関係を概念的に示す図。FIG. 3 is a vertical side view showing a state where the channel box is removed from the fuel assembly in the above-mentioned embodiment, conceptually showing an axial height relationship between a large diameter water rod, a large diameter multi-region poison rod and a drift short fuel rod. Fig.

【図４】（Ａ）は太径水棒の下流部で細径化しかつスペ
ーサと係合する位置で冷却水旋回機構を有し、さらにス
ペーサ保持片を取り付けた短尺管部の概念を説明する
図、（Ｂ）は水棒、毒物棒及び短尺燃料棒のうち、細径
化された部分に装着するもので、旋回機構ではなく側面
へ冷却水を偏流させるフロー制御材を示す図、（Ｃ）は
（Ａ）の変形例を示す図、（Ｄ）は旋回機構を有するフ
ロー制御材の一例を示す図。FIG. 4A illustrates the concept of a short pipe part having a cooling water swirl mechanism at a position where the diameter of the water rod is reduced in the downstream part and engaged with the spacer, and a spacer holding piece is further attached. FIG. 6B is a view showing a flow control member that is attached to a reduced diameter portion of a water rod, a poison rod, and a short fuel rod, and shows a flow control material that causes the cooling water to flow to the side surface instead of the swivel mechanism. 8A is a diagram showing a modified example of FIG. 9A, and FIG. 9D is a diagram showing an example of a flow control material having a turning mechanism.

【図５】前記実施例による太径水棒を示す図。FIG. 5 is a diagram showing a large diameter water rod according to the embodiment.

【図６】前記実施例による燃料棒と毒物棒とを示す図。FIG. 6 is a diagram showing a fuel rod and a poison rod according to the embodiment.

【図７】前記実施例による中実太径２領域毒物棒を示す
図。FIG. 7 is a view showing a solid large-diameter two-region poison stick according to the embodiment.

【図８】前記実施例による中水太径２領域毒物棒を示す
図。FIG. 8 is a view showing a medium-water large-diameter two-region poison stick according to the embodiment.

【図９】前記実施例による偏流短尺燃料棒を示す図。FIG. 9 is a view showing a drift short fuel rod according to the embodiment.

【図１０】本発明に係る燃料集合体の第２の実施例を示
す横断面図。FIG. 10 is a cross-sectional view showing a second embodiment of the fuel assembly according to the present invention.

【図１１】本発明に係る燃料集合体の第３の実施例を示
す横断面図。FIG. 11 is a cross sectional view showing a third embodiment of the fuel assembly according to the present invention.

【図１２】本発明に係る燃料集合体の第４の実施例を示
す横断面図。FIG. 12 is a cross sectional view showing a fourth embodiment of the fuel assembly according to the present invention.

【図１３】本発明に係る燃料集合体の第５の実施例を示
す横断面図。FIG. 13 is a cross sectional view showing a fifth embodiment of the fuel assembly according to the present invention.

【図１４】本発明に係る燃料集合体の第６の実施例を示
す横断面図。FIG. 14 is a cross sectional view showing a sixth embodiment of the fuel assembly according to the present invention.

【図１５】本発明に係る燃料集合体の第７の実施例を示
す横断面図。FIG. 15 is a cross sectional view showing a seventh embodiment of the fuel assembly according to the present invention.

【図１６】本発明に係る燃料集合体の第８の実施例を示
す横断面図。FIG. 16 is a cross sectional view showing an eighth embodiment of the fuel assembly according to the present invention.

【図１７】本発明に係る燃料集合体の第９の実施例を示
す横断面図。FIG. 17 is a cross sectional view showing a ninth embodiment of the fuel assembly according to the present invention.

【図１８】本発明に係る燃料集合体の第１０の実施例を
示す横断面図。FIG. 18 is a transverse sectional view showing a tenth embodiment of the fuel assembly according to the present invention.

【図１９】本発明に係る燃料集合体の第１１の実施例を
示す横断面図。FIG. 19 is a cross-sectional view showing an eleventh embodiment of the fuel assembly according to the present invention.

【図２０】本発明に係る燃料集合体の第１２の実施例を
示す横断面図。FIG. 20 is a cross-sectional view showing a twelfth embodiment of the fuel assembly according to the present invention.

【図２１】本発明に係る燃料集合体の第１３の実施例を
示す横断面図。FIG. 21 is a transverse sectional view showing a thirteenth embodiment of the fuel assembly according to the present invention.

【図２２】本発明に係る燃料集合体の第１４の実施例を
示す横断面図。FIG. 22 is a cross-sectional view showing a fourteenth embodiment of the fuel assembly according to the present invention.

【図２３】本発明に係る燃料集合体の第１５の実施例を
示す横断面図。FIG. 23 is a cross sectional view showing a fifteenth embodiment of the fuel assembly according to the present invention.

【図２４】図２３に示す実施例の変形例を示す図。FIG. 24 is a diagram showing a modification of the embodiment shown in FIG. 23.

【図２５】図２３に示す実施例の他の変形例を示す図。FIG. 25 is a diagram showing another modification of the embodiment shown in FIG. 23.

【図２６】（Ａ）は従来のＢＷＲ用燃料集合体を示す縦
断面図、（Ｂ）は燃料棒を示す図、（Ｃ）は太径水棒を
示す図。26A is a vertical sectional view showing a conventional BWR fuel assembly, FIG. 26B is a view showing a fuel rod, and FIG. 26C is a view showing a large-diameter water rod.

【図２７】（Ａ）は従来の同上燃料集合体を示す横断面
図、（Ｂ）は他の例を示す横断面図。27 (A) is a cross-sectional view showing a conventional fuel assembly of the same as above, and FIG. 27 (B) is a cross-sectional view showing another example.

【図２８】（Ａ）は燃料集合体からチャンネルボックス
を取り外した縦側面図、（Ｂ）はそれに対応した出力分
布図、（Ｃ）はボイド分布図。28A is a vertical side view of the fuel assembly with the channel box removed, FIG. 28B is an output distribution map corresponding thereto, and FIG. 28C is a void distribution map.

【符号の説明】[Explanation of symbols]

２０ 燃料集合体 ２０ａ 燃料バンドル ２１ チャンネルボックス ２２ 長尺燃料棒 ２３ 可燃性毒物棒 ２４ ペレット ２５ 金属管 ２６ 太径水棒 ２７ 中実太径２領域毒物棒 ２７ａ，２８ａ 外管 ２７ｂ，２８ｂ 内管 ２７ｃ，２８ｃ 円環状毒物ペレット ２７ｄ 芯毒物ペレット ２８ 中水太径２領域毒物棒 ２８ｄ 通水孔 ２９ 偏流短尺燃料棒 ３０ 細径管 ３１ 偏流機構 ３１ａ 偏流部材 ３２ 下部タイプレート ３３ 上部タイプレート ３４スペーサ ３５ 細径管 ３６ 短尺管 ３６ａ，３６ｂ テーパ部 ３７ 旋回羽根 ３８ フロー制御材 ４０ スリット状非沸騰水領域 ４１ 圧力管 20 Fuel Assembly 20a Fuel Bundle 21 Channel Box 22 Long Fuel Rod 23 Burnable Poison Rod 24 Pellet 25 Metal Tube 26 Large Diameter Water Rod 27 Solid Large Diameter 2 Region Poison Rod 27a, 28a Outer Tube 27b, 28b Inner Tube 27c , 28c Annular poison pellet 27d Core poison pellet 28 Medium water large diameter 2 area poison rod 28d Water passage hole 29 Distorted short fuel rod 30 Small-diameter pipe 31 Distortion mechanism 31a Dispersion member 32 Lower tie plate 33 Upper tie plate 34 Spacer 35 Thin Diameter tube 36 Short tube 36a, 36b Tapered portion 37 Swirling blade 38 Flow control material 40 Slit-shaped non-boiling water region 41 Pressure tube

───────────────────────────────────────────────────── 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 3/326 ＧＤＢ 3/62 ＧＤＢ Ｋ Ｇ２１Ｃ 3/30 ＧＤＢ Ｐ ＧＤＢ Ｋ ＧＤＢ Ｙ (72)発明者 光武 徹 神奈川県横浜市磯子区新杉田町８番地 株 式会社東芝横浜事業所内─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. 6 Identification code Internal reference number FI Technical display location G21C 3/326 GDB 3/62 GDB K G21C 3/30 GDB P GDB K GDB Y (72) Inventor Toru Mitsutake 8 Shinsita-cho, Isogo-ku, Yokohama-shi, Kanagawa Stock company Toshiba Yokohama office

Claims (8)

【特許請求の範囲】[Claims] 【請求項１】 燃料に可燃性毒物を添加しない多数の燃
料棒と、燃料に可燃性毒物を添加した複数の毒物棒と、
両端部の一定長さ範囲を除き前記燃料棒の径より大きい
径を有する少なくとも１本の太径水棒とを、複数のスペ
ーサ、上流側結合部材及び下流側結合部材を用いて格子
状に配列し一体化して燃料バンドルとした燃料集合体に
おいて、前記毒物棒の一部は両端部の一定長さ範囲を除
き前記燃料棒の直径より大きくかつ内部と外周部とで組
成を同一または異にする太径多領域毒物棒とし、この太
径多領域毒物棒の少なくとも１本は前記太径水棒に隣接
して配置し、かつ前記太径水棒とそれに隣接する前記太
径多領域毒物棒との集団を取り囲む配置で多数の燃料棒
を配設したことを特徴とする燃料集合体。1. A large number of fuel rods in which no burnable poison is added to the fuel, and a plurality of poison rods in which the burnable poison is added to the fuel,
At least one large-diameter water rod having a diameter larger than the diameter of the fuel rod except for a certain length range at both ends is arranged in a lattice using a plurality of spacers, an upstream-side coupling member and a downstream-side coupling member. In the fuel assembly integrated into a single fuel bundle, a part of the poison rod is larger than the diameter of the fuel rod except for a certain length range at both ends, and the composition is the same or different between the inside and the outside. A large-diameter multi-zone poison rod, at least one of the large-diameter multi-zone poison rods is disposed adjacent to the large-diameter water rod, and the large-diameter water rod and the large-diameter multi-zone poison stick adjacent thereto. The fuel assembly is characterized in that a large number of fuel rods are arranged so as to surround the group. 【請求項２】 太径水棒は、その管肉部に可燃性毒物を
含有してなることを特徴とする請求項１記載の燃料集合
体。2. The fuel assembly according to claim 1, wherein the large-diameter water rod contains a burnable poison in its tube wall portion. 【請求項３】 太径多領域毒物棒の少なくとも一部のも
のが、内部に冷却材を貫流させる冷却材貫流部を有する
ことを特徴とする請求項１記載の燃料集合体。3. The fuel assembly according to claim 1, wherein at least a part of the large-diameter multi-zone poison rod has a coolant flow-through portion through which the coolant flows. 【請求項４】 太径多領域毒物棒の少なくとも一部のも
のに添加された可燃性毒物の濃度が、その太径多領域毒
物棒の内部において高く、外周部において低いことを特
徴とする請求項１記載の燃料集合体。4. The concentration of the combustible poison added to at least a part of the large-diameter multi-zone poison rod is high inside the large-diameter multi-zone poison rod and low in the outer peripheral portion. The fuel assembly according to item 1. 【請求項５】 太径多領域毒物棒の少なくとも一部のも
のの内部に添加された可燃性毒物が硼素化合物であり、
外周部に添加された可燃性毒物がガドリニウム化合物で
あることを特徴とする請求項４記載の燃料集合体。5. The burnable poison added to the inside of at least a part of the large-diameter multi-zone poison rod is a boron compound,
The fuel assembly according to claim 4, wherein the burnable poison added to the outer peripheral portion is a gadolinium compound. 【請求項６】 太径水棒または太径多領域毒物棒の少な
くとも一部のものが、冷却材の流れの下流側から一定長
さ範囲に亘って細径化されており、その細径化された部
分でその部分に隣接する燃料棒の核分裂性核種の濃縮度
が天然ウランのウラン２３５の濃縮度より高い部分に、
冷却材の流れを隣接燃料棒の方向へ偏流させる偏流機構
を有することを特徴とする請求項１記載の燃料集合体。6. A large-diameter water rod or at least a part of a large-diameter multi-zone poison rod is thinned over a certain length range from the downstream side of the flow of the coolant, and the diameter is reduced. In the portion where the enrichment of fissionable nuclides in the fuel rod adjacent to that portion is higher than that of natural uranium 235,
The fuel assembly according to claim 1, further comprising a drift mechanism that biases the flow of the coolant toward the adjacent fuel rods. 【請求項７】 燃料に可燃性毒物を添加しない多数の燃
料棒と、燃料に可燃性毒物を添加した複数の毒物棒と、
両端部の一定長さ範囲を除き前記燃料棒の径より大きい
径を有する少なくとも１本の太径水棒とを、複数のスペ
ーサ、上流側結合部材及び下流側結合部材を用いて格子
状に配列し一体化して燃料バンドルとし、この燃料バン
ドルを取り囲む配置で金属製のチャンネルボックスを設
けてなる燃料集合体において、前記チャンネルボックス
に面した位置に配置された燃料棒または毒物棒は、冷却
水の流れの下流側端から一定長さ範囲に亘って細径化さ
れており、その細径化された部分でその部分に隣接する
燃料棒の核分裂性核種の濃縮度が天然ウランのウラン２
３５の濃縮度より高い部分に、冷却材の流れを隣接燃料
棒の方向へ偏流させる偏流機構を有することを特徴とす
る燃料集合体。7. A large number of fuel rods in which no burnable poison is added to the fuel, and a plurality of poison rods in which the burnable poison is added to the fuel,
At least one large-diameter water rod having a diameter larger than the diameter of the fuel rod except for a certain length range at both ends is arranged in a lattice using a plurality of spacers, an upstream-side coupling member and a downstream-side coupling member. In a fuel assembly in which a metal channel box is provided so as to surround the fuel bundle, a fuel rod or a poison rod disposed at a position facing the channel box is a cooling water. The uranium 2 of natural uranium has a reduced diameter over a certain length range from the downstream end of the flow, and the enriched concentration of the fissile nuclides of the fuel rods adjacent to the reduced diameter is 2
35. A fuel assembly characterized by having a drift mechanism for biasing the flow of the coolant in the direction of the adjacent fuel rods, in a portion of the fuel cell 35 having a higher concentration than that of 35. 【請求項８】 太径多領域毒物棒の下流側で細径化され
スペーサと係合する部分、チャンネルボックスに面した
燃料棒または毒物棒の下流側で細径化されスペーサと係
合する部分、および太径水棒の下流側で細径化されスペ
ーサと係合する部分のうち、少くともいずれかの部分
に、細径化されていない部分の直径と略同じ外径を持つ
短尺管を装着したことを特徴とする請求項６または７記
載の燃料集合体。8. A portion of a large-diameter multi-zone poison rod that is reduced in diameter downstream side and engages with a spacer, and a portion of a fuel rod facing a channel box or a portion of a poison rod that is reduced in diameter downstream side and engages with a spacer. , And a portion of the portion that is reduced in diameter on the downstream side of the large diameter water rod and engages with the spacer, at least one of the portions has a short pipe with an outer diameter that is approximately the same as the diameter of the non-thinned portion. The fuel assembly according to claim 6, which is mounted.
JP10560794A 1994-05-19 1994-05-19 Fuel assembly Expired - Lifetime JP3292587B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP10560794A JP3292587B2 (en) 1994-05-19 1994-05-19 Fuel assembly

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP10560794A JP3292587B2 (en) 1994-05-19 1994-05-19 Fuel assembly

Publications (2)

Publication Number Publication Date
JPH07311291A true JPH07311291A (en) 1995-11-28
JP3292587B2 JP3292587B2 (en) 2002-06-17

Family

ID=14412196

Family Applications (1)

Application Number Title Priority Date Filing Date
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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6061416A (en) * 1997-02-13 2000-05-09 Hitachi, Ltd. Fuel assembly
US20130070885A1 (en) * 2006-09-06 2013-03-21 Krishna P. Singh Canister apparatus and basket for transporting, storing and/or supporting spent nuclear fuel
KR20160015482A (en) * 2014-07-30 2016-02-15 울산과학기술원 산학협력단 Fuel assembly with wire-wraps having different arrangement and/or coiling rotation
EP3547329B2 (en) † 2018-03-30 2023-03-15 Hitachi-Ge Nuclear Energy, Ltd. Fuel assembly
KR20230045970A (en) * 2021-09-29 2023-04-05 한국과학기술원 Cold shutdown system for SCO2-cooled ship-propulsion fast reactor

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6335956B1 (en) 1988-02-12 2002-01-01 Hitachi, Ltd. Fuel assembly
US6061416A (en) * 1997-02-13 2000-05-09 Hitachi, Ltd. Fuel assembly
US20130070885A1 (en) * 2006-09-06 2013-03-21 Krishna P. Singh Canister apparatus and basket for transporting, storing and/or supporting spent nuclear fuel
US8929504B2 (en) * 2006-09-06 2015-01-06 Holtec International, Inc. Canister apparatus and basket for transporting, storing and/or supporting spent nuclear fuel
US10026514B2 (en) * 2006-09-06 2018-07-17 Holtec International, Inc. Canister apparatus and basket for transporting, storing and/or supporting spent nuclear fuel
KR20160015482A (en) * 2014-07-30 2016-02-15 울산과학기술원 산학협력단 Fuel assembly with wire-wraps having different arrangement and/or coiling rotation
EP3547329B2 (en) † 2018-03-30 2023-03-15 Hitachi-Ge Nuclear Energy, Ltd. Fuel assembly
US11728046B2 (en) 2018-03-30 2023-08-15 Hitachi-Ge Nuclear Energy, Ltd. Fuel assembly
KR20230045970A (en) * 2021-09-29 2023-04-05 한국과학기술원 Cold shutdown system for SCO2-cooled ship-propulsion fast reactor

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