JP2004340580A

JP2004340580A - Lower tie plate, method for assembling it and fuel assembly

Info

Publication number: JP2004340580A
Application number: JP2003133938A
Authority: JP
Inventors: Takao Kageyama; 隆夫影山; Akira Tanabe; 朗田辺; Yuji Iwamoto; 優二岩本; Yasuhiro Masuhara; 康博増原; Takanori Fukahori; 貴憲深堀; Akihiro Yamanaka; 章広山中
Original assignee: Global Nuclear Fuel Japan Co Ltd
Current assignee: Global Nuclear Fuel Japan Co Ltd
Priority date: 2003-05-13
Filing date: 2003-05-13
Publication date: 2004-12-02
Anticipated expiration: 2023-05-13
Also published as: JP4090940B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lower tie plate, a method for assembling it and fuel assemblies which can improve the performance of catching linear and slender foreign bodies. <P>SOLUTION: The lower tie plate has a network part 7 for holding the lower parts of fuel rods 2 so that they can be laid out in a lattice form at intervals between them respectively, a nozzle part 8 which extends downward from the circumference of the network part 7 to form a lower tie plate cavity 9 below the network part 7 and has an inlet opening 10 at its lower end, a partition board 30 which is horizontally located below the network part 7 in the lower tie plate cavity 9 to divide it into upper and lower parts and cylindrical filters 32 which are mounted on the partition board 30 and have opening parts below and above them. In the fuel rods 2, lower end plugs 11 including rod-shaped parts extending downward are located. The upper parts of the cylindrical filters 32 are placed so as to surround the rod-shaped parts, and the space between them is almost plugged up. Opening parts 39 of the cylindrical filters 32 above the partition board 30 are placed mainly on lateral faces of the cylindrical filters 32. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、軽水型原子炉用の燃料集合体の下部タイプレート、特に、冷却材中に混入した異物が燃料部に流入するのを阻止・抑制できるようにした下部タイプレートとその下部タイプレートの組み立て方法に関し、さらにその下部タイプレートを利用した燃料集合体に関する。
【０００２】
【従来の技術】
沸騰水型原子炉用の燃料集合体は、例えば図２３に示すように、ほぼ正方形の断面を有する筒形のチャンネルボックス１を有し、このチャンネルボックス１内に正方格子状に配列された複数の燃料棒２と少なくとも１本のウォータロッド３が収容されている。この燃料集合体の上下部にはそれぞれ上部タイプレート４および下部タイプレート５が装着されている。ウォータロッド３には、その軸方向に所定の間隔をおいて複数のスペーサ６（図２３では一つだけを示す）が取り付けられ、このスペーサ６によって燃料棒２が整列・支持されている。
【０００３】
下部タイプレート５は、燃料棒２およびウォータロッド３を直接的に固定・支持するネットワーク部７と、ネットワーク部７の周辺部から下方に延びるノズル部８とを有し、これらによって、ネットワーク部７の下方に下部タイプレート空洞９が形成されている。ノズル部８の下部には下部タイプレート入口開口１０が形成されている。
【０００４】
各燃料棒２は被覆管の中に複数の燃料ペレットを充填したものであるが（図示せず）、この被覆管の下端部を閉じる栓として下部端栓１１がある。燃料棒の下部端栓１１の下部は細い円柱の棒状になっていて、この部分が下部タイプレートのネットワーク部７のボス４０（図１、２等参照）に設けられた挿入孔１３に挿入され、それによって燃料棒の下部端栓１１が支持されている。
【０００５】
一方、ウォータロッド３は中空の金属管であって、チャンネルボックス１内の下部タイプレート５のわずか上方に入口孔２６が設けられ、上部タイプレート４のわずか下方に出口孔２７が設けられている。入口孔２６から液相の冷却材がウォータロッド３内に流入し、液相のままの冷却材がウォータロッド３内を上昇して、出口孔２７から流出するようになっている。
【０００６】
このウォータロッド３の下端部にも燃料棒の下部端栓１１とほぼ同様の構造の下部端栓１２があり、下部端栓１２の下部は細い円柱の棒状になっていて、この部分が下部タイプレートのネットワーク部７に設けられた挿入孔１３に挿入され、それによってウォータロッドの下部端栓１２が支持されている。
【０００７】
下部タイプレートのネットワーク部７には、下部端栓１１、１２が挿入されてそれらの下部端栓１１、１２を支持する挿入孔１３を有するボス４０と、ボス４０同士を水平方向に連絡するウェブ４１（図１、２等参照）があって、ウェブ４１の間の流通孔を冷却材が通り抜けられるようになっている。
【０００８】
図２３の燃料集合体で、冷却材１５は、下部タイプレート入口開口１０から、下部タイプレート空洞９内に入り、ネットワーク部７の流通孔を通り抜けて、チャンネルボックス１内の燃料棒２およびウォータロッド３の周辺へと流れ、上部タイプレート４を通って燃料集合体の外へ出ていく。
【０００９】
なお、図２３に示すように、下部タイプレートノズル部８の側面には微小なリークホール１７が設けられており、下部タイプレート空洞９内の冷却材１５のうちの若干量がチャンネルボックス１の外側へ流れるようになっている。
【００１０】
近年の高性能化された燃料集合体では、燃料集合体内部に異物が侵入するのを防ぐことを目的としてフィルタ機能を付加するものもある。例えば、下部タイプレートのネットワーク部の流通孔の口径を従来よりも小さく約５ｍｍとすることにより、流れに対する抵抗を増加（即ち、高圧損化）する設計もあり、これによって炉心の安定性の改善が図られているが、これは異物フィルタの役目も果たしている。
【００１１】
燃料集合体に侵入することが予想される異物としては、プラント建設時に原子炉一次系内に僅かに残された金屑、機器洗浄時の金属性ブラシの折れ片、機器損傷時の破片等が想定されている。その形状も、板状、弦巻バネ状（螺旋状）、針金状（直線状）等、多岐にわたることが予想されている。
【００１２】
図２４は、異物フィルタ機能を有する下部タイプレートの例を示す（例えば特開平７−３０６２８４号公報参照）。図２４で、燃料棒２とウォータロッド３の下部端栓１１、１２の下部が、下部タイプレート５のネットワーク部７の挿入孔１３を貫通している。ネットワーク部７の下方には、異物フィルタの機能を有する仕切り板２０が、下部タイプレート空洞９を横断してほぼ水平に設けられている。仕切り板２０には、図２５に示すように、燃料棒２とウォータロッド３の各下部端栓１１、１２が通る貫通孔２１、２２のほかに、冷却材が流通し、異物の流通を阻止する小孔２４が多数設けられている。
【００１３】
図２４の構成で、冷却材１５は、下部タイプレート入口開口１０から下部タイプレート空洞９内に流入し、仕切り板２０の小孔２４を通り、さらにネットワーク部７の流通孔を通って、チャンネルボックス１内の燃料棒２およびウォータロッド３の周辺へと流れる。このとき、冷却材１５中の異物は、仕切り板２０の小孔２４を通り抜けにくいので、チャンネルボックス１内への異物流入が抑制される。
【００１４】
【発明が解決しようとする課題】
従来の異物フィルタを有する下部タイプレートでは、炉心入口部に達した異物を炉心内に侵入することをある程度の確率で防止することはできた。しかしながら、従来の仕切り板２０の小孔２４を通ってネットワーク部７の流通孔を通る流れは、ほぼ鉛直上向きの直線状である。このため、特に直線的な細長い異物が冷却材によって流れに対して縦方向に運ばれたときに、これらの流路を通過してしまう可能性がないとはいえなかった。
本発明の目的は、特に直線的な細長い異物の捕捉性能にすぐれた下部タイプレートとその組み立て方法ならびに燃料集合体を提供することにある。
【００１５】
【課題を解決するための手段】
本発明は上記目的を達成するものであって、請求項１に記載の発明は、原子燃料を充填した複数の燃料棒が互いに間隔をあけて格子状に配列されるようにそれらの燃料棒の下部を保持するネットワーク部と、このネットワーク部の周囲から下方に延びてこのネットワーク部の下方に下部タイプレート空洞を形成し、下端に入口開口を有するノズル部と、前記下部タイプレート空洞内の前記ネットワーク部の下方にほぼ水平に配置されて前記下部タイプレート空洞を上下に区画する仕切り板と、前記仕切り板に取り付けられてその仕切り板の下方および上方に開口部を有する複数の筒状フィルタと、を有する下部タイプレートであって、前記複数の燃料棒の少なくとも一部には下方に延びる棒状部を含む下部端栓が配置され、前記複数の筒状フィルタの上部は前記棒状部を囲むように配置され、その筒状フィルタの上部と前記棒状部の間はほぼ閉塞されており、前記仕切り板の上方にある前記筒状フィルタの開口部はおもに前記筒状フィルタの側面に設けられていること、を特徴とする。
請求項１に記載の発明によれば、特に直線的な細長い異物の捕捉性能にすぐれた下部タイプレートを提供できる。
【００１６】
また、請求項２に記載の発明は、請求項１に記載の下部タイプレートにおいて、あらかじめ前記仕切り板に前記筒状フィルタを取り付けた後に、前記仕切り板と、前記ネットワ−ク部と、前記ノズル部とを互いに結合してなること、を特徴とする。
請求項２に記載の発明によれば、請求項１に記載の発明による作用・効果が得られるほか、筒状フィルタの形状を柔軟に選択することができ、組み立ても容易である。
【００１７】
また、請求項３に記載の発明は、請求項１に記載の下部タイプレートにおいて、前記仕切り板が前記ネットワ−ク部と前記ノズル部との間に配置されるようにあらかじめ形成されたものに、前記ノズル部の前記入口開口から挿入された前記筒状フィルタが取り付けられてなること、を特徴とする。
【００１８】
請求項３に記載の発明によれば、請求項１に記載の発明による作用・効果が得られるほか、下部タイプレートの以外の部分を従来と同様の方法で組み立てることができ、これに筒状フィルタを取り付ける作業を追加するだけですむ。
【００１９】
また、請求項４に記載の発明は、請求項３に記載の下部タイプレートにおいて、前記複数の筒状フィルタを相互に結合して複数の筒状フィルタの群を構成するための複数の連結棒があって、前記仕切り板の下面に、前記連結棒を着脱可能な係合部を有すること、を特徴とする。
【００２０】
請求項４に記載の発明によれば、請求項３に記載の発明による作用・効果が得られるほか、複数の筒状フィルタをあらかじめ結合しておくので、筒状フィルタの取り付け作業の省力ができる。さらに、筒状フィルタを着脱できるので、原子炉の定期点検のときなどに、必要に応じて筒状フィルタを交換するなどの保守が容易である。
【００２１】
また、請求項５に記載の発明は、請求項１ないし４のいずれかに記載の下部タイプレートにおいて、前記筒状フィルタは、円筒形状であること、を特徴とする。
請求項５に記載の発明によれば、請求項１ないし４に記載の発明による作用・効果が得られるほか、筒状フィルタの製造が容易である。
【００２２】
また、請求項６に記載の発明は、請求項１ないし４のいずれかに記載の下部タイプレートにおいて、前記複数の燃料棒は正方格子状に配列され、前記筒状フィルタは、前記正方格子の向きに合わせて配置された四角筒形状であること、を特徴とする。
【００２３】
請求項６に記載の発明によれば、請求項１ないし４に記載の発明による作用・効果が得られるほか、筒状フィルタを多数配列したときに全体の流路面積を大きくとることができる。
【００２４】
また、請求項７に記載の発明は、請求項１ないし４のいずれかに記載の下部タイプレートにおいて、前記筒状フィルタは、先細形状のものと末広がり形状のものが交互に配置されていること、を特徴とする。
【００２５】
請求項７に記載の発明によれば、請求項１ないし４に記載の発明による作用・効果が得られるほか、筒状フィルタを多数配列したときに全体の流路面積を大きくとることができ、また、冷却材中の異物がフィルタに捕捉された場合に、その異物が下部タイプレートの下に落下することを抑制することができる。
【００２６】
また、請求項８に記載の発明は、請求項１ないし７のいずれかに記載の下部タイプレートにおいて、前記筒状フィルタの側面に設けられた開口部は円形であること、を特徴とする。
請求項８に記載の発明によれば、請求項１ないし４に記載の発明による作用・効果が得られるほか、筒状フィルタの製造が容易である。
【００２７】
また、請求項９に記載の発明は、原子燃料を充填した複数の燃料棒が互いに間隔をあけて格子状に配列されるようにそれらの燃料棒の下部を保持するネットワーク部と、このネットワーク部の周囲から下方に延びてこのネットワーク部の下方に下部タイプレート空洞を形成し、下端に入口開口を有するノズル部と、前記下部タイプレート空洞内の前記ネットワーク部の下方にほぼ水平に配置されて前記下部タイプレート空洞を上下に区画する仕切り板と、前記仕切り板に取り付けられてその仕切り板の下方および上方に開口部を有する複数の筒状フィルタと、を有する下部タイプレートであって、前記複数の燃料棒の少なくとも一部には下方に延びる棒状部を含む下部端栓が配置され、前記複数の筒状フィルタの上部は前記棒状部を囲むように配置され、その筒状フィルタの上部と前記棒状部の間はほぼ閉塞されており、前記仕切り板の上方にある前記筒状フィルタの開口部はおもに前記筒状フィルタの側面に設けられている下部タイプレートの組み立て方法において、前記複数の筒状フィルタを前記仕切り板に固定する第１の工程と、前記第１の工程の後に、前記仕切り板を前記ネットワーク部と前記ノズル部との間に挟み込むようにして相互に結合する第２の工程と、を有すること、を特徴とする。
【００２８】
請求項９に記載の発明によれば、特に直線的な細長い異物の捕捉性能にすぐれた下部タイプレートを提供でき、しかも、筒状フィルタの形状を柔軟に選択することができ、組み立ても容易である。
【００２９】
また、請求項１０に記載の発明は、原子燃料を充填した複数の燃料棒が互いに間隔をあけて格子状に配列されるようにそれらの燃料棒の下部を保持するネットワーク部と、このネットワーク部の周囲から下方に延びてこのネットワーク部の下方に下部タイプレート空洞を形成し、下端に入口開口を有するノズル部と、前記下部タイプレート空洞内の前記ネットワーク部の下方にほぼ水平に配置されて前記下部タイプレート空洞を上下に区画する仕切り板と、前記仕切り板に取り付けられてその仕切り板の下方および上方に開口部を有する複数の筒状フィルタと、を有する下部タイプレートであって、前記複数の燃料棒の少なくとも一部には下方に延びる棒状部を含む下部端栓が配置され、前記複数の筒状フィルタの上部は前記棒状部を囲むように配置され、その筒状フィルタの上部と前記棒状部の間はほぼ閉塞されており、前記仕切り板の上方にある前記筒状フィルタの開口部はおもに前記筒状フィルタの側面に設けられている下部タイプレートの組み立て方法において、前記仕切り板が前記ネットワーク部と前記ノズル部との間に配置されるように形成する第１の工程と、前記第１の工程の後に、前記筒状フィルタを前記ノズル部の前記入口開口から挿入して前記仕切り板に取り付ける第２の工程と、を有すること、を特徴とする。
【００３０】
請求項１０に記載の発明によれば、特に直線的な細長い異物の捕捉性能にすぐれた下部タイプレートを提供でき、しかも、下部タイプレートの以外の部分を従来と同様の方法で組み立てることができ、これに筒状フィルタを取り付ける作業を追加するだけですむ。
【００３１】
また、請求項１１に記載の発明は、請求項１０に記載の下部タイプレートの組み立て方法において、前記第２の工程の前に、前記筒状フィルタの複数個を、前記ノズル部の前記入口開口から挿入可能な範囲で相互に結合して、複数の筒状フィルタ群をあらかじめ作る第３の工程をさらに有すること、を特徴とする。
【００３２】
請求項１１に記載の発明によれば、請求項１０に記載の発明による作用・効果が得られるほか、複数の筒状フィルタをあらかじめ結合しておくので、フィルタの取り付け作業の省力ができる。
【００３３】
また、請求項１２に記載の発明は、請求項１０または１１に記載の下部タイプレートの組み立て方法において、前記仕切り板の下面には凹凸が設けられており、前記第２の工程は、前記仕切り板の下面の前記凹凸に前記筒状フィルタを嵌め込む工程を含むこと、を特徴とする。
請求項１２に記載の発明によれば、請求項１０または１１に記載の発明による作用・効果が得られるほか、フィルタの取り付け作業の省力ができる。
【００３４】
また、請求項１３に記載の発明は、原子燃料を充填した複数の燃料棒と、内部に冷却材が通る少なくとも１本のウォータロッドと、前記燃料棒およびウォータロッドの上部を保持する上部タイプレートと、前記燃料棒およびウォータロッドの下部を保持する下部タイプレートと、を有する燃料集合体において、前記下部タイプレートは、前記燃料棒およびウォータロッドが互いに間隔をあけて格子状に配列されるようにそれらの燃料棒およびウォータロッドの下部を保持するネットワーク部と、このネットワーク部の周囲から下方に延びてこのネットワーク部の下方に下部タイプレート空洞を形成し、下端に入口開口を有するノズル部と、前記下部タイプレート空洞内の前記ネットワーク部の下方にほぼ水平に配置されて前記下部タイプレート空洞を上下に区画する仕切り板と、前記仕切り板に取り付けられてその仕切り板の下方および上方に開口部を有する複数の筒状フィルタと、を有し、前記燃料棒およびウォータロッドの少なくとも一部の下部には下方に延びる棒状部を含む下部端栓が取り付けられていて、前記複数の筒状フィルタの上部は前記下部端栓の棒状部を囲むように配置され、その筒状フィルタの上部と前記下部端栓の棒状部の間はほぼ閉塞されており、前記仕切り板の上方にある前記筒状フィルタの開口部はおもに前記筒状フィルタの側面に設けられていること、を特徴とする。
請求項１３に記載の発明によれば、特に直線的な細長い異物の捕捉性能にすぐれた燃料集合体を提供できる。
【００３５】
また、請求項１４に記載の発明は、請求項１３に記載の燃料集合体において、前記下部端栓の少なくとも一つの内部には、冷却材流路である下部端栓流路が形成されていて、その下部端栓流路の入口は、前記仕切部材よりも下方にあって下方を向いて開口し、またその下部端栓流路の出口は、前記筒状フィルタの上方にあって水平方向に開口していること、を特徴とする。
【００３６】
請求項１４に記載の発明によれば、請求項１３に記載の発明による作用・効果が得られるほか、下部端栓流路によって全体の流路面積が大きく取れ、圧力損失を低減できる。
【００３７】
また、請求項１５に記載の発明は、請求項１３または１４に記載の燃料集合体において、前記下部端栓の少なくとも一つの下端から上方に延びる少なくとも一つの切り込みが形成されていること、を特徴とする。
【００３８】
請求項１５に記載の発明によれば、請求項１３または１４に記載の発明による作用・効果が得られるほか、切り込みによって冷却材中の異物の捕捉確率を高めることができる。
【００３９】
また、請求項１６に記載の発明は、原子燃料を充填した複数の燃料棒と、内部に冷却材が通る少なくとも１本のウォータロッドと、前記燃料棒およびウォータロッドの上部を保持する上部タイプレートと、前記燃料棒およびウォータロッドの下部を保持する下部タイプレートと、を有する燃料集合体において、前記下部タイプレートは、前記燃料棒およびウォータロッドが互いに間隔をあけて格子状に配列されるようにそれらの燃料棒およびウォータロッドの下部を保持するネットワーク部と、このネットワーク部の周囲から下方に延びてこのネットワーク部の下方に下部タイプレート空洞を形成し、下端に入口開口を有するノズル部と、前記下部タイプレート空洞内の前記ネットワーク部の下方にほぼ水平に配置されて前記下部タイプレート空洞を上下に区画する仕切り板と、前記燃料棒およびウォータロッドの真下の位置で前記仕切り板に取り付けられ、その仕切り板の下方および上方に開口部を有する複数の筒状フィルタと、を有し、前記仕切り板の上方にある前記筒状フィルタの開口部はおもに前記筒状フィルタの側面に設けられており、前記燃料棒およびウォータロッドの少なくとも一部の下部には下方に延びる棒状部を含む下部端栓が取り付けられていて、この棒状部の下端は前記筒状フィルタの上端よりも高い位置にあり、この棒状部の下端に下向きの入口開口部を有しその上方に水平方向を向いた出口開口部を有する下部端栓流路が下部端栓内に形成されていること、を特徴とする。
請求項１６に記載の発明によれば、特に直線的な細長い異物の捕捉性能にすぐれた燃料集合体を提供できる。
【００４０】
【発明の実施の形態】
以下、図１〜図２２を参照しながら本発明に係る原子燃料集合体用の下部タイプレートの実施の形態を説明する。ただし、従来の技術と、あるいは互いに、共通もしくは類似の部分には、共通の符号を付して、重複説明は適宜省略する。
【００４１】
まず、図１〜図５を参照して本発明の第１の実施の形態を説明する。この実施の形態では、図１に示すように、下部タイプレートは従来の一体形成のものではなく、ネットワーク部７と、ノズル部８とが別個の部品としてそれぞれ鋳造され、これらの間に、水平な板状の仕切り板３０を挟み込んで、これらを、例えば溶接によって互いに接合する。
【００４２】
下部端栓１１、１２が仕切り板３０を通り抜ける部分に、下部端栓１１、１２を囲むようにして筒状フィルタ３２が配置され、これらの筒状フィルタ３２は仕切り板３０の開口３５（図２参照）に取り付けられている。筒状フィルタ３２と仕切り板３０の取り付け部は、少なくとも冷却材中の異物が通り抜けない程度に隙間なく構成され、仕切り板３０には開口３５のほかに開口は設けられていない。仕切り板３０の厚みは例えば２ｍｍである。なお、図１では、チャンネルボックス１（図１８）を示すのを省略している。
【００４３】
図２〜図５に示すように、フィルタ３２は、寸法が例えば、直径１２ｍｍ、高さ２０ｍｍで、下面は開放していて、仕切り板３０の開口３５を覆うように、仕切り板３０に取り付けられている。フィルタ３２の上面３６には下部端栓１１、１２の棒状部が貫通する円形の穴３７が設けられている。穴３７の直径は例えば７．２ｍｍであって、下部端栓１１、１２と穴３７の間の間隙は、冷却材中の異物が通り抜けない程度に小さくなっている。フィルタ３２の側面３８には、複数の孔３９が設けられている。孔３９は例えば円形であってその直径は、例えば約２ｍｍである。なお、孔３９の形状は、円形のほか、多角形、星型など種々のものがありうる。
【００４４】
個々の円筒状フィルタ３２の中心軸は、下部端栓１１、１２の中心軸と一致するように、例えば図５に示すように配置されている。なお、図２、図４等で、燃料棒の下部端栓１１が示されているが、ウォータロッドの下部端栓１２でも全く同様である。
【００４５】
下部タイプレートの組み立てにあたっては、あらかじめ、図５に示すように仕切り板３０にフィルタ３２を取り付けておき、その後、ネットワーク部７とノズル部８の間に仕切り板３０を挟み込むようにして、溶接によって相互に接合する。
【００４６】
本実施の形態で、例えば、長さが２０ｍｍ〜３０ｍｍの針金状の異物（図示せず）が、冷却材１５とともに下部タイプレート入口開口１０から下部タイプレート空洞９内に侵入した場合、仕切り板３０の開口３５からフィルタ３２内に上向きに流れて入る。冷却材１５の流れはフィルタ３２内で向きを変えて水平方向になり、孔３９から仕切り板３０の上方の空間に出る。このとき、異物は向きを変えにくいので、異物が、孔３９を通ってフィルタ３２の外に出る可能性は非常に小さい。小片板状の異物も、フィルタ３２で止められる。
【００４７】
また、プラントの機器不具合時に万が一大量の異物が発生した場合でも、必要な冷却材流量を確保する可能性を高めることができることができる。さらに、燃料集合体を原子炉心外に取り出す際に、捕獲した異物を、燃料集合体とともに原子炉外に取り出すことができる。また、フィルタ部は構造上信頼度が高く、フィルタ部自体が異物となって燃料集合体チャンネル内に侵入することを防止することができる。
【００４８】
次に、図６および図７を参照して、本発明の第２の実施の形態を説明する。この実施の形態では、第１および第２の円錐台状フィルタ４５、４６が仕切り板３０の上に交互に配置されて固定されている。第１の円錐台状フィルタ４５は下方が太くなっており、第２の円錐台状フィルタ４６は下方が細くなっている。なお、この明細書では、これらの円錐台状フィルタも含めて「筒状フィルタ」と呼ぶ。
【００４９】
仕切り板３０の、第１の円錐台状フィルタ４５および第２の円錐台状フィルタ４６との取り付け部にはそれぞれ、第１の開口４７、第２の開口４８が形成されている（図７参照）。第１の円錐台状フィルタ４５は下方が太くなっており、第２の円錐台状フィルタ４６は下方が細くなっていることから、第１の開口４７の方が第２の開口４８よりも大きくなっている。仕切り板３０と第１および第２の円錐台状フィルタ４５、４６との取り付け部は、少なくとも冷却材中の異物が通り抜けない程度に隙間なく構成され、仕切り板３０には開口４７、４８のほかに開口は設けられていない。
【００５０】
第１の円錐台状フィルタ４５は、第１の実施の形態における円筒状フィルタ３２と同様に、下部端栓１１、１２の棒状部の周りに配置され、下部端栓１１、１２の下端は仕切り板３０の第１の開口４７を貫通してその下方まで延びている。第１の円錐台状フィルタ４５の上部は次第に細くなっていて、その上端には下部端栓１１、１２の棒状部が通れる穴４９が形成されている。穴４９の直径は、下部端栓１１、１２の棒状部の直径（例えば７ｍｍ）よりも僅かに大きい。第１の円錐台状フィルタ４５の側面５０には、複数の孔３９が形成されている。第１の円錐台状フィルタ４５は上面を覆う板部が不要であり、フィルタ製作が簡単化される。
【００５１】
第２の円錐台状フィルタ４６では、その中央に配置される下部端栓１１ａの下端が第２の円錐台状フィルタ４６内にあって、仕切り板３０の開口４８に達していない。第２の円錐台状フィルタ４６の上面５１には下部端栓１１ａの棒状部が貫通する穴５２が設けられている。第２の円錐台状フィルタ４６の側面５３には、複数の孔３９が形成されている。この第２の円錐台状フィルタ４６では、一旦フィルタ４６に捕捉された異物が、フィルタ４６の入口より外に（下方に）出にくくなるという利点がある。
【００５２】
上記第２の実施の形態の変形例として、第１の円錐台状フィルタ４５と第２の円錐台状フィルタ４６を交互に配列する代わりに、その他の任意の配列としたり、一方だけの配列とすることも可能である。
【００５３】
次に、図８ないし図１０を参照して、本発明の第３の実施の形態を説明する。この実施の形態では、フィルタ５６は、横断面が正方形の四角筒状である。正方形の一辺の長さは例えば１２ｍｍであり、四角筒の高さは例えば２０ｍｍである。また、各側面部５７には、例えば高さ４ｍｍ、幅８ｍｍの長方形の窓５８が２個ずつ開けられている。フィルタ部上面５９には、下部端栓１１、１２の棒状部が貫通する正方形の穴６０が形成されている。この実施の形態における下部端栓１１、１２の棒状部（図示せず）は断面が例えば一辺が４ｍｍの正方形であって、穴６０との隙間は、冷却材中の異物が通り抜けない程度に小さくなっている。
【００５４】
図に示す実施の形態では、フィルタ５６は仕切り板３０を貫通して、その途中で固定されている。側面部５７の窓５８はいずれも仕切り板３０より上方に設けられている。また、フィルタ５６の下端は開放している。下部端栓１１、１２の棒状部はフィルタ５６の中央を貫通してフィルタ５６の下端より下方まで延びている。
【００５５】
この第３の実施の形態では、図１０に示すように、断面が正方形のフィルタ５６が水平面内に正格子状に配列され、しかも各側面部５７の向きを配列の方向に合わせて配置する。このため、フィルタ５６の流路面積を大きくとることができ、第１、第２の実施の形態に比べてフィルタ部で発生する圧力損失を減少させることができる。また、側面部５７の窓５８は、第１、第２の実施の形態における孔３９よりも大きな流路面積をとることができ、そのことからも圧力損失を減少させることができる。
【００５６】
なお、上記各実施の形態の変形例として、第１または第２の実施の形態と、第３の実施の形態の特徴を部分的に任意に組み合わせることができる（図示せず）。例えば、第１または第２の実施の形態における孔３９を図８および図９に示すような側面部の大きな窓５８で置き替えることも可能である。また、第３の実施の形態で、図８および図１０に示す穴６０を円形に変えて、通常の円形断面の下部端栓１１、１２の棒状部と組み合わせて使用することも可能である。さらに、第３の実施の形態で、フィルタ５６を図９に示すように仕切り板３０を貫通させる代わりに、第１、第２の実施の形態と同様に仕切り板３０の開口の上方にフィルタ５６を被せるようにしてもよい。
【００５７】
次に、図１１ないし図１３を参照して、本発明の第４の実施の形態を説明する。この実施の形態では、フィルタ６５は、第１の実施の形態（図１〜図５）におけるフィルタ３２とほぼ同様の円筒形状であるが、仕切り板３０の開口の上方に配置するのでなく、仕切り板３０の円形の開口６６を途中まで貫通した状態に配置されている。
【００５８】
この実施の形態では、初めに、仕切り板３０をネットワーク部７とノズル部８の間に挟み込むようにして、溶接によって相互に接合する。そして、その後、ノズル部８の入口開口１０からフィルタ６５を挿入して、これを仕切り板３０に取り付ける。
【００５９】
図１２に示すように、フィルタ６５は隣接する複数個が連結棒６７によって互いに水平方向に結合され、複数（図１２の例では９個）の群をなしている。これらの群はそれぞれ、ノズル部８の入口開口１０を通して挿入できる大きさであって、例えば、図１２に示すように３行３列を基本とする。
【００６０】
図１３に示すように、仕切り板３０の下面には連結棒６７を嵌め込むことができる溝６８が形成されている。またこの溝６８ができるように、溝６８を挟んでそれぞれ二つの凸部６９が形成されている。溝６８は、すべての連結棒６７に対応する位置に形成してもよいが、フィルタ６５の各群を保持できるものであれば、図１３に示すように、連結棒６７の数よりも溝６８の数を少なくしてもよい。
【００６１】
この実施の形態では、下部タイプレートのフィルタ６５以外の部分をあらかじめ組み立てておき、後からフィルタ６５を挿入して組み立てることができる。また、燃料交換時等に、異物を捕捉したフィルタ６５を取り外して新しいフィルタに取り替えることもできる。
【００６２】
また、この実施の形態では、複数のフィルタ６５を連結棒６７によってあらかじめ複数の群に結合しておき、これらの群をノズル部８の入口開口１０を通して挿入して仕切り板３０に取り付ける。このため、各フィルタ６５を個々に仕切り板３０に取り付ける場合に比べて、フィルタ６５の取り付け作業を省力化できる。ここで、複数のフィルタ６５を連結棒６７によって結合する作業は広い場所でできるので比較的容易な作業であり、自動化も比較的容易であるのに対して、フィルタ６５を仕切り板３０に取り付ける作業はノズル部８の入口開口１０を通して行なうので、比較的困難な作業である。
【００６３】
なお、第４の実施の形態の変形例として、複数のフィルタ６５を連結棒６７によって結合することをせず、各フィルタ６５を個々に仕切り板３０に取り付けることも可能である（図示せず）。その場合、連結棒６７を仕切り板３０の溝６８に嵌める代わりに、各フィルタ６５を個々に取り付けることのできる凹凸（図示せず）を仕切り板３０に設ける必要がある。
【００６４】
さらに、第４の実施の形態の変形例として、ネットワーク部７と仕切り板３０とノズル部８とを溶接によって相互に接合する構造とせず、これらを一体として例えば鋳造することも可能である。すなわち、下部タイプレートのフィルタ６５以外の部分をあらかじめ組み立てておき、後からフィルタ６５を挿入して組み立てるものだからである。このようにすれば、下部タイプレートのフィルタ６５以外の部分を組み立てる工程は従来と同様の工程とすることができる。
上記第４の実施の形態の組み立て方法で、フィルタは必ずしも円筒形でなくともよく、図６〜図９に示す他の形状のフィルタに適用してもよい。
【００６５】
次に、図１４ないし図１６を参照して、本発明の第５の実施の形態を説明する。この実施の形態では、一つの下部タイプレートで、種々のフィルタを組み合わせたものとして示してある。すなわち、第１の実施の形態におけるフィルタ３２があるとともに、その他のフィルタも有している。
【００６６】
図１５に示すように、下部端栓７２の棒状部に縦穴７３を設けたものが含まれている。縦穴７３の下端は仕切り板３０の下方にあって下向きに開口している。また、縦穴７３の上端には横穴７４が接続されていて、横穴７４は仕切り板３０の上方で横向きに開口している。下部端栓７２の棒状部の外側を囲んで、円筒状フィルタ７５が配置されている。円筒状フィルタ７５は、第１の実施の形態におけるフィルタ３２とほぼ同様のものであって、下端８２は開放しており、上端８３は閉じている。また、側面の仕切り板３０の上方には複数の孔３９が設けられている。
【００６７】
冷却材１５は、円筒状フィルタ７５の内面と下部端栓７２の棒状部外面の間の環状部のほか、棒状部の縦穴７３内にも入って上昇流を形成する。それらの流れのいずれもが上昇方向から水平方向に流れの向きを変えるので、そこで冷却材中の異物を捕捉することができる。下部端栓の棒状部内に流路がない場合に比べて流路面積を大きくとることができるので、圧力損失を小さくすることができる。
【００６８】
なお、図１４に示すように、上記穴明きの下部端栓７２を単独で、すなわちフィルタ７５を伴わないで配置するものがあってもよい。
また、図１６に示すように、下部端栓７７の棒状部は短くなっていてその下端は仕切り板３０の上方に位置し、この下部端栓７７には下端に開口のある縦穴７８と、縦穴７８の上端に接続されて横向きに開口する横穴７９が形成されている。この下部端栓７７の下方には、円錐台状のフィルタ８０が配置されている。フィルタ８０はその途中まで仕切り板３０を貫通して仕切り板３０に取り付けられていて、下端８５は開放しており、上端８６は閉じている。また、側面の仕切り板３０の上方には複数の孔３９が設けられている。下部端栓７７の棒状部の下端とフィルタ８０の上端との間には間隔があいている。
【００６９】
さらに、図１４に示すように、下部端栓と干渉しない位置の仕切り板３０の上にフィルタ８８を配置することもできる。このフィルタ８８は断面が円形または正方形の筒状のもので、フィルタ８０と同様に、途中まで仕切り板３０を貫通する状態で仕切り板３０に取り付けられている。下端は開放していて、上端は閉じている。側面には比較的大きな横長の窓８９が設けられている。このように種々の形状のフィルタ機能を組み合わせることにより、多様な形状の異物に対応することができ、かつ、流路閉塞が発生する可能性を減らすことができる。
【００７０】
次に、図１５に示した第５の実施の形態における下部端栓７２とフィルタ７５の種々の変形例を、図１７〜図２２を参照して説明する。
図１７に示す例では、下部端栓９２の棒状部の外径は例えば７ｍｍであって、下部端栓棒状部の下部に、鉛直方向に幅０．５ｍｍ、長さ２ｃｍの切り込み９３が１本設けられている。そして、切り込み９３の上方に、棒状部の側面から斜め上向きに延びる幅０．５ｍｍ、長さ３ｍｍの切り込み９４が４本設けられている。
【００７１】
図１８に示す例では、下部端栓９６の棒状部の外径は例えば７ｍｍであって、下部端栓棒状部の下部に、鉛直方向に幅０．５ｍｍ、長さ２ｃｍの切り込み９７が２本設けられている。そして、２本の切り込み９７によって挟まれた中央部９８が切り込み９７の外側の外側部９９よりも長く延びている。これにより、異物は、切り込み部に挟まり捕獲される可能性が高まる。
【００７２】
図１９に示す例では、図１５の例とほぼ同様に、下部端栓１０２の棒状部の外径は例えば７ｍｍであって、下部端栓棒状部の中央の鉛直方向に直径が４ｍｍの下端開放の縦穴７３が設けられている。この縦穴７３の上端に横穴７４が接続されていて、横穴７４はフィルタ７５の上端よりも上方で開口している。図１９の例では、下部端栓１０２の下端から、鉛直方向に幅０．５ｍｍ、長さ２ｃｍの切り込み１０３を２本入れている。これにより、冷却材中の異物は、切り込み１０３に挟まって捕獲する可能性を高めることができる上に、流路閉塞の可能性を減少させることができる。
【００７３】
図２０に示す例は図１９の例の変形であって、下部端栓１０５の棒状部の縦穴７３の途中に水平方向の貫通孔１０６が複数個形成されている。これにより、冷却材中の異物が流路を閉塞させる可能性をさらに減少させることができる。
【００７４】
図２１に示す例では、下部端栓１０７の棒状部の外径は例えば７ｍｍである。その外側に、例えば直径１２ｍｍ、長さが２５ｍｍの円筒状フィルタ７５が配置され、仕切り板３０に固定されている。下部端栓１０７の棒状部の外側の仕切り板３０より上方の部分に、鉛直方向に深さ１．５ｍｍの溝１０８が４本形成されており、これによって、フィルタ７５の上面３６の穴３７の内側に流路が形成される。この流路自体は上向きに開いているが、ここを通る流路はその前後で必ず曲り部を通るので、特に、針金状の異物を捕獲することができる。その上、流路閉塞の可能性を減少させることができる。
【００７５】
図２２に示す例では、直径１２ｍｍ、長さが３２ｍｍの円筒状フィルタ１１０が仕切り板３０に取り付けられている。フィルタ１１０の下端１１１は仕切り板３０の下面よりも５ｍｍ下方にあり、フィルタの側面１１２に、下端１１１から鉛直方向に、深さ２ｍｍ、長さ２５ｍｍの溝１１３を４本設ける。これにより、仕切り板３０の下方からの流れに対する流路を確保している。フィルタの側面１１２には、溝１１３を周方向に取り囲むように、幅２ｍｍの円環１１４が取り付けられている。これにより、特に、針金状の異物を捕獲することができる上に、流路閉塞の可能性を減少させることができる。
【００７６】
以上、本発明に係る下部タイプレートの種々の実施の形態を示した。これらの各実施の形態の種々の特徴を任意に組み合わせることも可能である。例えば図１５〜図２２で下部端栓や筒状フィルタの平断面形状が円形になっているのを、図８〜図１０のように正方形で置き換えることも考えられる。また、一つの下部タイプレートで、種々のフィルタまたは下部端栓を組み合わせて配置することも可能である。
【００７７】
【発明の効果】
以上述べたように、本発明のフィルタが取り付けられた仕切り板を有する下部タイプレートを採用することにより、異物を炉心入口部で捕捉することの確実性を向上させることができる。
【００７８】
また、板状、つるまきバネ状（らせん状）、針金状（直線状）等の多様な形状の異物を捕捉することが可能となり、異物が原因となる燃料破損に対する信頼性が向上し、プラントの運転性能が改善される。
【図面の簡単な説明】
【図１】本発明に係る下部タイプレートとその周辺の第１の実施の形態の模式的立断面図。
【図２】図１の下部タイプレートの要部拡大立断面図。
【図３】図１のフィルタを１個だけ仕切り板に取り付けた状態を示す部分的斜視図。
【図４】図１のフィルタを１個だけ仕切り板に取り付けた状態を示す立面図。
【図５】図１のフィルタを仕切り板に取り付けた状態を示す平面図。
【図６】本発明に係る下部タイプレートとその周辺の第２の実施の形態の模式的立断面図。
【図７】図６の下部タイプレートの要部拡大立断面図。
【図８】本発明に係る下部タイプレートの第３の実施の形態における角筒状フィルタの取り付け前の状態を示す斜視図。
【図９】図８のフィルタを１個だけ仕切り板に取り付けた状態を示す立面図。
【図１０】図８のフィルタを仕切り板に取り付けた状態を示す平面図。
【図１１】本発明に係る下部タイプレートとその周辺の第４の実施の形態の模式的立断面図。
【図１２】図１１のＸ− Ｘ線矢視底面図。
【図１３】図１１のフィルタ取り付け前の状態におけるＸ− Ｘ線矢視底面図。
【図１４】本発明に係る下部タイプレートとその周辺の第５の実施の形態の模式的立断面図。
【図１５】（ａ）は図１４のＹ部拡大立断面図、（ｂ）は（ａ）のＢ−Ｂ線矢視底断面図。
【図１６】（ａ）は図１４のＺ部拡大立断面図、（ｂ）は（ａ）のＢ−Ｂ線矢視底面図。
図１４のＺ部拡大立断面図。
【図１７】図１５に示す下部端栓とフィルタの組合せの他の例を示す図であって、（ａ）は立断面図、（ｂ）は（ａ）のＢ−Ｂ線矢視底断面図。
【図１８】図１５に示す下部端栓とフィルタの組合せのさらに他の例を示す図であって、（ａ）は立断面図、（ｂ）は（ａ）のＢ−Ｂ線矢視底断面図。
【図１９】図１５に示す下部端栓とフィルタの組合せのさらに他の例を示す図であって、（ａ）は立断面図、（ｂ）は（ａ）のＢ−Ｂ線矢視底断面図。
【図２０】図１５に示す下部端栓とフィルタの組合せのさらに他の例を示す図であって、（ａ）は立断面図、（ｂ）は（ａ）のＢ−Ｂ線矢視底断面図。
【図２１】図１５に示す下部端栓とフィルタの組合せのさらに他の例を示す図であって、（ａ）は立断面図、（ｂ）は（ａ）のＢ−Ｂ線矢視平断面図、（ｃ）は（ａ）のＣ−Ｃ線矢視平断面図。
【図２２】図１５に示す下部端栓とフィルタの組合せのさらに他の例を示す図であって、（ａ）は立断面図、（ｂ）は（ａ）のＢ−Ｂ線矢視平断面図、（ｃ）は（ａ）のＣ−Ｃ線矢視平断面図。
【図２３】従来の燃料集合体の全体立断面図。
【図２４】図２３の下部タイプレートとその周辺の拡大立断面図。
【図２５】図２３の仕切り板だけを取り出して示す平面図。
【符号の説明】
１…チャンネルボックス、２…燃料棒、３…ウォータロッド、４…上部タイプレート、５…下部タイプレート、６…スペーサ、７…ネットワーク部、８…ノズル部、９…下部タイプレート空洞、１０…下部タイプレート入口開口、１１，１１ａ…燃料棒の下部端栓、１２…ウォータロッドの下部端栓、１３…挿入孔、１５…冷却材、１７…リークホール、２０…仕切り板、２１…燃料棒の下部端栓が通る貫通孔、２２…ウォータロッドの下部端栓が通る貫通孔、２４…小孔、２６…ウォータロッドの入口孔、２７…ウォータロッドの出口孔、３０…仕切り板、３２…円筒状フィルタ、３５…開口、３７…穴、３８…側面、３９…孔、４０…ボス、４１…ウェブ、４５…第１の円錐台状フィルタ、４６…第２の円錐台状フィルタ、４７…第１の開口、４８…第２の開口、４９…穴、５０…側面、５１…上面、５２…穴、５３…側面、５６…フィルタ、５７…側面部、５８…窓、５９…フィルタ上面、６０…穴、６５…フィルタ、６６…開口、６７…連結棒、６８…溝、６９…凸部、７２…下部端栓、７３…縦穴、７４…横穴、７５…円筒状フィルタ、７７…下部端栓、７８…縦穴、７９…横穴、８０…フィルタ、８２…下端、８３…上端、８５…下端、８６…上端、８８…フィルタ、８９…窓、９２…下部端栓、９３…切り込み、９４…切り込み、９６…下部端栓、９７…切り込み、９９…外側部、１０２…下部端栓、１０３…切り込み、１０５…下部端栓、１０６…貫通孔、１０７…下部端栓、１０８…溝、１１０…円筒状フィルタ、１１１…下端、１１２…側面、１１３…溝、１１４…円環。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a lower tie plate of a fuel assembly for a light water reactor, and more particularly to a lower tie plate and a lower tie plate capable of preventing and suppressing foreign substances mixed in a coolant from flowing into a fuel section. And a fuel assembly using the lower tie plate.
[0002]
[Prior art]
A fuel assembly for a boiling water reactor has, for example, as shown in FIG. 23, a cylindrical channel box 1 having a substantially square cross section, and a plurality of fuel cells arranged in a square lattice in the channel box 1. Fuel rod 2 and at least one water rod 3 are accommodated. An upper tie plate 4 and a lower tie plate 5 are mounted on the upper and lower portions of the fuel assembly, respectively. A plurality of spacers 6 (only one is shown in FIG. 23) are attached to the water rod 3 at predetermined intervals in the axial direction, and the fuel rods 2 are aligned and supported by the spacers 6.
[0003]
The lower tie plate 5 has a network portion 7 for directly fixing and supporting the fuel rod 2 and the water rod 3 and a nozzle portion 8 extending downward from a peripheral portion of the network portion 7. The lower tie plate cavity 9 is formed below the lower tie plate. A lower tie plate inlet opening 10 is formed below the nozzle portion 8.
[0004]
Each fuel rod 2 has a cladding tube filled with a plurality of fuel pellets (not shown), and there is a lower end plug 11 as a stopper for closing the lower end of the cladding tube. The lower portion of the lower end plug 11 of the fuel rod has a thin cylindrical rod shape, and this portion is inserted into an insertion hole 13 provided in a boss 40 (see FIGS. 1 and 2) of the network portion 7 of the lower tie plate. Thereby, the lower end plug 11 of the fuel rod is supported.
[0005]
On the other hand, the water rod 3 is a hollow metal tube, and the inlet hole 26 is provided slightly above the lower tie plate 5 in the channel box 1, and the outlet hole 27 is provided slightly below the upper tie plate 4. . The coolant in the liquid phase flows into the water rod 3 from the inlet hole 26, and the coolant in the liquid phase rises in the water rod 3 and flows out from the outlet hole 27.
[0006]
At the lower end of the water rod 3, there is also a lower end plug 12 having substantially the same structure as the lower end plug 11 of the fuel rod. The lower portion of the lower end plug 12 is formed in a thin cylindrical rod shape, and this portion is a lower type. The lower end plug 12 of the water rod is supported by an insertion hole 13 provided in the rate network portion 7.
[0007]
A boss 40 having lower end plugs 11, 12 inserted therein and having an insertion hole 13 for supporting the lower end plugs 11, 12 is provided in the lower tie plate network section 7, and a web for horizontally connecting the bosses 40 to each other. 41 (see FIGS. 1 and 2 and the like) so that the coolant can pass through the flow holes between the webs 41.
[0008]
In the fuel assembly of FIG. 23, the coolant 15 enters the lower tie plate cavity 9 from the lower tie plate inlet opening 10, passes through the flow hole of the network section 7, and passes through the fuel rod 2 and the water in the channel box 1. It flows around the rod 3 and exits the fuel assembly through the upper tie plate 4.
[0009]
As shown in FIG. 23, a small leak hole 17 is provided on the side surface of the lower tie plate nozzle section 8, and a small amount of the coolant 15 in the lower tie plate cavity 9 is formed in the channel box 1. It flows outward.
[0010]
Some recent high performance fuel assemblies have a filter function added for the purpose of preventing foreign substances from entering the fuel assembly. For example, there is a design in which the diameter of the flow hole of the network portion of the lower tie plate is made smaller than the conventional one to about 5 mm to increase the resistance to the flow (that is, to reduce the high pressure), thereby improving the stability of the core. However, this also serves as a foreign matter filter.
[0011]
Foreign materials that are expected to enter the fuel assembly include gold scraps slightly left in the reactor primary system during plant construction, broken pieces of metallic brushes during equipment cleaning, and debris from equipment damage. It is assumed. It is expected that the shape may be various, such as a plate shape, a helical spring shape (spiral shape), and a wire shape (linear shape).
[0012]
FIG. 24 shows an example of a lower tie plate having a foreign matter filter function (for example, see Japanese Patent Application Laid-Open No. 7-306284). In FIG. 24, the lower portions of the lower end plugs 11 and 12 of the fuel rod 2 and the water rod 3 pass through the insertion holes 13 of the network portion 7 of the lower tie plate 5. Below the network section 7, a partition plate 20 having the function of a foreign matter filter is provided substantially horizontally across the lower tie plate cavity 9. As shown in FIG. 25, in addition to the through holes 21 and 22 through which the lower end plugs 11 and 12 of the fuel rod 2 and the water rod 3 pass, coolant flows through the partition plate 20 to prevent foreign matter from flowing. Many small holes 24 are provided.
[0013]
In the configuration of FIG. 24, the coolant 15 flows into the lower tie plate cavity 9 from the lower tie plate inlet opening 10, passes through the small holes 24 of the partition plate 20, further passes through the flow holes of the network section 7, and passes through the channel. It flows around the fuel rod 2 and the water rod 3 in the box 1. At this time, foreign matter in the coolant 15 is unlikely to pass through the small holes 24 of the partition plate 20, so that foreign matter flowing into the channel box 1 is suppressed.
[0014]
[Problems to be solved by the invention]
In a lower tie plate having a conventional foreign matter filter, foreign matter that has reached the core entrance can be prevented from entering the core with a certain probability. However, the flow passing through the small hole 24 of the conventional partition plate 20 and the flow hole of the network portion 7 is a straight line that is substantially vertically upward. For this reason, it cannot be said that there is no possibility of passing through these flow paths, particularly when linear and elongated foreign matter is carried by the coolant in the vertical direction with respect to the flow.
SUMMARY OF THE INVENTION An object of the present invention is to provide a lower tie plate having excellent linear and elongated foreign matter trapping performance, a method of assembling the lower tie plate, and a fuel assembly.
[0015]
[Means for Solving the Problems]
The present invention achieves the above-mentioned object, and the invention according to claim 1 has a structure in which a plurality of fuel rods filled with nuclear fuel are arranged so as to be arranged in a grid at intervals. A network portion for holding the lower portion, a lower portion extending from the periphery of the network portion to form a lower tie plate cavity below the network portion, and a nozzle portion having an inlet opening at a lower end, and the nozzle portion in the lower tie plate cavity. A partition plate that is disposed substantially horizontally below the network unit and vertically partitions the lower tie plate cavity, and a plurality of cylindrical filters that are attached to the partition plate and have openings below and above the partition plate. A lower end plug including a downwardly extending rod-shaped portion is arranged on at least a part of the plurality of fuel rods, and the plurality of cylindrical rods are provided. The upper part of the filter is arranged so as to surround the rod-shaped part, and the space between the upper part of the cylindrical filter and the rod-shaped part is substantially closed, and the opening part of the cylindrical filter above the partition plate is mainly The filter is provided on a side surface of the cylindrical filter.
According to the first aspect of the present invention, it is possible to provide a lower tie plate having excellent linear and elongated foreign matter capturing performance.
[0016]
According to a second aspect of the present invention, in the lower tie plate according to the first aspect, after the cylindrical filter is attached to the partition plate in advance, the partition plate, the network portion, and the nozzle And the parts are connected to each other.
According to the second aspect of the invention, the operation and effect of the first aspect of the invention can be obtained, and the shape of the cylindrical filter can be flexibly selected, and the assembly is easy.
[0017]
According to a third aspect of the present invention, in the lower tie plate of the first aspect, the partition plate is formed in advance so as to be disposed between the network portion and the nozzle portion. And the cylindrical filter inserted from the inlet opening of the nozzle portion is attached.
[0018]
According to the third aspect of the present invention, the operation and effect of the first aspect of the present invention can be obtained, and the portions other than the lower tie plate can be assembled in the same manner as in the related art. All you have to do is add the work of installing the filter.
[0019]
According to a fourth aspect of the present invention, in the lower tie plate according to the third aspect, a plurality of connecting rods for connecting the plurality of tubular filters to each other to form a group of a plurality of tubular filters. There is provided an engaging portion on the lower surface of the partition plate to which the connecting rod can be attached and detached.
[0020]
According to the fourth aspect of the present invention, the operation and effect of the third aspect of the present invention can be obtained, and a plurality of cylindrical filters are connected in advance, so that the work of attaching the cylindrical filters can be saved. . Further, since the cylindrical filter can be attached and detached, maintenance such as replacement of the cylindrical filter as necessary at the time of periodic inspection of the nuclear reactor or the like is easy.
[0021]
According to a fifth aspect of the present invention, in the lower tie plate according to any one of the first to fourth aspects, the tubular filter has a cylindrical shape.
According to the fifth aspect of the invention, the functions and effects of the first to fourth aspects of the invention are obtained, and the manufacture of the cylindrical filter is easy.
[0022]
According to a sixth aspect of the present invention, in the lower tie plate according to any one of the first to fourth aspects, the plurality of fuel rods are arranged in a square lattice, and the cylindrical filter is formed of a square lattice. It is a quadrangular cylindrical shape arranged in accordance with the direction.
[0023]
According to the invention set forth in claim 6, the functions and effects of the inventions set forth in claims 1 to 4 can be obtained, and the overall flow passage area can be increased when a large number of cylindrical filters are arranged.
[0024]
According to a seventh aspect of the present invention, in the lower tie plate according to any one of the first to fourth aspects, the cylindrical filters are arranged such that a tapered filter and a divergent filter are alternately arranged. , Is characterized.
[0025]
According to the seventh aspect of the present invention, in addition to the functions and effects of the first to fourth aspects of the present invention, when a large number of cylindrical filters are arranged, the entire flow passage area can be increased, Further, when foreign matter in the coolant is captured by the filter, the foreign matter can be prevented from falling below the lower tie plate.
[0026]
According to an eighth aspect of the present invention, in the lower tie plate according to any one of the first to seventh aspects, an opening provided on a side surface of the cylindrical filter is circular.
According to the invention described in claim 8, the functions and effects of the inventions described in claims 1 to 4 can be obtained, and the manufacture of the cylindrical filter is easy.
[0027]
According to a ninth aspect of the present invention, there is provided a network unit for holding a lower portion of a plurality of fuel rods filled with nuclear fuel such that the plurality of fuel rods are arranged in a grid at intervals. A lower tie plate cavity extending downward from the periphery of the network portion to form a lower tie plate cavity below the network portion, and a nozzle portion having an inlet opening at a lower end, and disposed substantially horizontally below the network portion in the lower tie plate cavity. A lower tie plate, comprising: a partition plate that partitions the lower tie plate cavity up and down; and a plurality of cylindrical filters attached to the partition plate and having openings below and above the partition plate. A lower end plug including a rod portion extending downward is disposed on at least a part of the plurality of fuel rods, and an upper portion of the plurality of cylindrical filters surrounds the rod portion. The cylindrical filter is disposed, and the upper part of the cylindrical filter and the rod-like part are substantially closed, and the opening of the cylindrical filter above the partition plate is mainly provided on the side surface of the cylindrical filter. In the method of assembling a tie plate, a first step of fixing the plurality of tubular filters to the partition plate, and after the first step, sandwiching the partition plate between the network unit and the nozzle unit. And a second step of mutually coupling in such a manner.
[0028]
According to the ninth aspect of the present invention, it is possible to provide a lower tie plate having particularly excellent linear and elongated foreign matter capturing performance, and furthermore, it is possible to flexibly select the shape of the cylindrical filter, and it is easy to assemble. is there.
[0029]
Further, the invention according to claim 10 is a network unit that holds a lower part of a plurality of fuel rods filled with nuclear fuel such that the plurality of fuel rods are arranged in a grid at intervals. A lower tie plate cavity extending downward from the periphery of the network portion to form a lower tie plate cavity below the network portion, and a nozzle portion having an inlet opening at a lower end, and disposed substantially horizontally below the network portion in the lower tie plate cavity. A lower tie plate, comprising: a partition plate that partitions the lower tie plate cavity up and down; and a plurality of cylindrical filters attached to the partition plate and having openings below and above the partition plate. A lower end plug including a rod portion extending downward is disposed on at least a part of the plurality of fuel rods, and an upper portion of the plurality of cylindrical filters surrounds the rod portion. And the space between the upper part of the cylindrical filter and the rod-shaped part is substantially closed, and the opening part of the cylindrical filter above the partition plate is provided mainly on the side surface of the cylindrical filter. In the method of assembling the lower tie plate, a first step of forming the partition plate so as to be disposed between the network section and the nozzle section, and after the first step, the cylindrical filter is formed. A second step of inserting from the inlet opening of the nozzle portion and attaching to the partition plate.
[0030]
According to the tenth aspect of the present invention, it is possible to provide a lower tie plate having an excellent linear and elongated foreign matter trapping performance, and to assemble portions other than the lower tie plate by a conventional method. It is only necessary to add the work of attaching the cylindrical filter to this.
[0031]
According to an eleventh aspect of the present invention, in the method of assembling a lower tie plate according to the tenth aspect, before the second step, a plurality of the cylindrical filters are connected to the inlet opening of the nozzle portion. And a third step of forming a plurality of cylindrical filter groups in advance by mutually coupling in a range in which the filter can be inserted.
[0032]
According to the eleventh aspect, the function and effect of the tenth aspect can be obtained, and since a plurality of cylindrical filters are connected in advance, the labor for mounting the filters can be reduced.
[0033]
According to a twelfth aspect of the present invention, in the method of assembling the lower tie plate according to the tenth or eleventh aspect, the lower surface of the partition plate is provided with irregularities, and the second step includes the step of forming the partition. A step of fitting the cylindrical filter into the irregularities on the lower surface of the plate.
According to the twelfth aspect of the invention, the operation and effect of the tenth or eleventh aspect can be obtained, and labor for mounting the filter can be saved.
[0034]
According to a thirteenth aspect of the present invention, there is provided an upper tie plate which holds a plurality of fuel rods filled with nuclear fuel, at least one water rod through which a coolant passes, and an upper part of the fuel rod and the water rod. And a lower tie plate that holds the lower portions of the fuel rods and water rods, wherein the lower tie plate is arranged such that the fuel rods and water rods are arranged in a grid at intervals. A network portion that holds the lower portions of the fuel rods and the water rods, a nozzle portion that extends downward from the periphery of the network portion, forms a lower tie plate cavity below the network portion, and has an inlet opening at the lower end. The lower tie plate disposed substantially horizontally below the network portion within the lower tie plate cavity. A partition plate that partitions the cavity up and down, and a plurality of cylindrical filters attached to the partition plate and having openings below and above the partition plate, and at least a part of the fuel rod and the water rod. A lower end plug including a rod portion extending downward is attached to a lower portion of the lower end plug, and the upper portions of the plurality of cylindrical filters are arranged so as to surround the rod portion of the lower end plug. The space between the rod-shaped portions of the lower end plug is substantially closed, and an opening of the cylindrical filter above the partition plate is mainly provided on a side surface of the cylindrical filter.
According to the thirteenth aspect of the present invention, it is possible to provide a fuel assembly having excellent linear and elongated foreign matter trapping performance.
[0035]
According to a fourteenth aspect of the present invention, in the fuel assembly according to the thirteenth aspect, a lower end plug channel that is a coolant channel is formed inside at least one of the lower end plugs. The inlet of the lower end plug flow path is below the partition member and opens downward, and the outlet of the lower end plug flow path is above the tubular filter and extends horizontally. Characterized by being open.
[0036]
According to the fourteenth aspect of the present invention, the operation and effect of the thirteenth aspect of the present invention can be obtained, and the lower end plug flow path can provide a large flow area and reduce pressure loss.
[0037]
According to a fifteenth aspect of the present invention, in the fuel assembly according to the thirteenth or fourteenth aspect, at least one notch extending upward from at least one lower end of the lower end plug is formed. And
[0038]
According to the fifteenth aspect, the operation and effect of the thirteenth or fourteenth aspect can be obtained, and in addition, the probability of trapping foreign matter in the coolant can be increased by the cut.
[0039]
The invention according to claim 16 provides a plurality of fuel rods filled with nuclear fuel, at least one water rod through which a coolant passes, and an upper tie plate that holds upper portions of the fuel rod and the water rod. And a lower tie plate that holds the lower portions of the fuel rods and water rods, wherein the lower tie plate is arranged such that the fuel rods and water rods are arranged in a grid at intervals. A network portion that holds the lower portions of the fuel rods and the water rods, a nozzle portion that extends downward from the periphery of the network portion, forms a lower tie plate cavity below the network portion, and has an inlet opening at the lower end. The lower tie plate disposed substantially horizontally below the network portion within the lower tie plate cavity. A partition plate for partitioning the cavity up and down, and a plurality of cylindrical filters attached to the partition plate at positions directly below the fuel rods and the water rods and having openings below and above the partition plate. An opening of the cylindrical filter above the partition plate is provided mainly on a side surface of the cylindrical filter, and includes a rod-like portion extending downward at a lower part of at least a part of the fuel rod and the water rod. A lower end plug is attached, and the lower end of the rod portion is located higher than the upper end of the cylindrical filter, and has a downward inlet opening at the lower end of the rod portion and has a horizontal direction above it. A lower end plug passage having an outlet opening is formed in the lower end plug.
According to the sixteenth aspect of the present invention, it is possible to provide a fuel assembly having particularly excellent linear and elongated foreign matter capturing performance.
[0040]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a lower tie plate for a nuclear fuel assembly according to the present invention will be described with reference to FIGS. However, common or similar parts to those of the related art or to each other are denoted by common reference numerals, and redundant description is omitted as appropriate.
[0041]
First, a first embodiment of the present invention will be described with reference to FIGS. In this embodiment, as shown in FIG. 1, the lower tie plate is not a conventional one-piece, but the network part 7 and the nozzle part 8 are cast as separate parts, and a horizontal part is provided between them. These flat plate-shaped partition plates 30 are sandwiched, and these are joined to each other by, for example, welding.
[0042]
At the portion where the lower end plugs 11 and 12 pass through the partition plate 30, cylindrical filters 32 are arranged so as to surround the lower end plugs 11 and 12, and these cylindrical filters 32 are formed by openings 35 of the partition plate 30 (see FIG. 2). Attached to. An attachment portion between the cylindrical filter 32 and the partition plate 30 is formed without a gap so that at least foreign matter in the coolant does not pass through. The partition plate 30 has no opening other than the opening 35. The thickness of the partition plate 30 is, for example, 2 mm. In FIG. 1, the illustration of the channel box 1 (FIG. 18) is omitted.
[0043]
As shown in FIGS. 2 to 5, the filter 32 has a size of, for example, a diameter of 12 mm and a height of 20 mm, has a lower surface open, and is attached to the partition plate 30 so as to cover the opening 35 of the partition plate 30. ing. The upper surface 36 of the filter 32 is provided with a circular hole 37 through which the rod portions of the lower end plugs 11 and 12 pass. The diameter of the hole 37 is, for example, 7.2 mm, and the gap between the lower end plugs 11, 12 and the hole 37 is so small that foreign matter in the coolant does not pass through. A plurality of holes 39 are provided in the side surface 38 of the filter 32. The hole 39 is, for example, circular and has a diameter of, for example, about 2 mm. The shape of the hole 39 may be various shapes such as a polygon, a star, and the like in addition to a circle.
[0044]
The central axis of each cylindrical filter 32 is arranged, for example, as shown in FIG. 5 so as to coincide with the central axis of the lower end plugs 11 and 12. Although the lower end plug 11 of the fuel rod is shown in FIGS. 2 and 4 and the like, the same applies to the lower end plug 12 of the water rod.
[0045]
In assembling the lower tie plate, a filter 32 is attached to the partition plate 30 in advance as shown in FIG. 5, and then the partition plate 30 is sandwiched between the network section 7 and the nozzle section 8 by welding. Join with each other.
[0046]
In the present embodiment, for example, when a wire-like foreign matter (not shown) having a length of 20 mm to 30 mm enters the lower tie plate cavity 9 from the lower tie plate inlet opening 10 together with the coolant 15, the partition plate The fluid flows upward from the opening 35 into the filter 32. The flow of the coolant 15 changes its direction in the filter 32 to become horizontal, and exits from the hole 39 into the space above the partition plate 30. At this time, since it is difficult to change the direction of the foreign matter, the possibility that the foreign matter goes out of the filter 32 through the hole 39 is very small. The small plate-like foreign matter is also stopped by the filter 32.
[0047]
Further, even in the event that a large amount of foreign matter is generated in the event of a plant malfunction, the possibility of securing a necessary coolant flow rate can be increased. Further, when the fuel assembly is taken out of the reactor core, the captured foreign matter can be taken out of the reactor together with the fuel assembly. Further, the filter portion has a high structural reliability, and can prevent the filter portion itself from becoming a foreign substance and entering the fuel assembly channel.
[0048]
Next, a second embodiment of the present invention will be described with reference to FIGS. In this embodiment, first and second truncated conical filters 45 and 46 are alternately arranged and fixed on the partition plate 30. The first truncated conical filter 45 is thicker at the bottom, and the second truncated cone filter 46 is thinner at the lower part. In this specification, these frusto-conical filters are also referred to as “cylindrical filters”.
[0049]
A first opening 47 and a second opening 48 are formed at the mounting portions of the partition plate 30 with the first truncated cone filter 45 and the second truncated cone filter 46, respectively. ). The first frusto-conical filter 45 is thicker at the bottom and the second frustum-shaped filter 46 is thinner at the bottom. Therefore, the first opening 47 is larger than the second opening 48. Has become. Attachment portions between the partition plate 30 and the first and second truncated conical filters 45 and 46 are configured without gaps at least to such an extent that foreign matter in the coolant does not pass through. No opening is provided.
[0050]
The first frusto-conical filter 45 is disposed around the rod-shaped portions of the lower end plugs 11, 12 similarly to the cylindrical filter 32 in the first embodiment, and the lower ends of the lower end plugs 11, 12 are partitioned. It extends through the first opening 47 of the plate 30 and below it. The upper part of the first truncated conical filter 45 is gradually narrower, and the upper end thereof is formed with a hole 49 through which the rod-shaped parts of the lower end plugs 11 and 12 can pass. The diameter of the hole 49 is slightly larger than the diameter (for example, 7 mm) of the rod portion of the lower end plugs 11 and 12. A plurality of holes 39 are formed in the side surface 50 of the first truncated conical filter 45. The first truncated conical filter 45 does not require a plate portion that covers the upper surface, and the filter fabrication is simplified.
[0051]
In the second truncated conical filter 46, the lower end of the lower end plug 11 a disposed at the center thereof is inside the second truncated conical filter 46, and does not reach the opening 48 of the partition plate 30. The upper surface 51 of the second truncated conical filter 46 is provided with a hole 52 through which the rod portion of the lower end plug 11a penetrates. A plurality of holes 39 are formed in the side surface 53 of the second truncated conical filter 46. The second frusto-conical filter 46 has the advantage that foreign matter once captured by the filter 46 is less likely to come out (downward) from the inlet of the filter 46.
[0052]
As a modified example of the second embodiment, instead of alternately arranging the first truncated conical filters 45 and the second truncated conical filters 46, any other arrangement or an arrangement of only one of them may be used. It is also possible.
[0053]
Next, a third embodiment of the present invention will be described with reference to FIGS. In this embodiment, the filter 56 is in the shape of a square tube having a square cross section. The length of one side of the square is, for example, 12 mm, and the height of the square tube is, for example, 20 mm. In addition, two rectangular windows 58 each having a height of 4 mm and a width of 8 mm are opened in each side surface portion 57, for example. A square hole 60 through which the rod-shaped portions of the lower end plugs 11 and 12 penetrate is formed in the filter portion upper surface 59. The rod-like portions (not shown) of the lower end plugs 11 and 12 in this embodiment have a cross section of, for example, a square having a side of 4 mm, and the gap with the hole 60 is so small that foreign matter in the coolant does not pass through. Has become.
[0054]
In the embodiment shown in the figure, the filter 56 penetrates the partition plate 30 and is fixed in the middle thereof. Each of the windows 58 of the side surface portion 57 is provided above the partition plate 30. The lower end of the filter 56 is open. The rod portions of the lower end plugs 11 and 12 pass through the center of the filter 56 and extend below the lower end of the filter 56.
[0055]
In the third embodiment, as shown in FIG. 10, filters 56 each having a square cross section are arranged in a regular lattice in a horizontal plane, and the direction of each side surface 57 is arranged in accordance with the arrangement direction. Therefore, the flow path area of the filter 56 can be increased, and the pressure loss generated in the filter section can be reduced as compared with the first and second embodiments. Further, the window 58 of the side surface portion 57 can have a larger flow area than the hole 39 in the first and second embodiments, which can reduce the pressure loss.
[0056]
As a modification of the above embodiments, the features of the first or second embodiment and the features of the third embodiment can be partially and arbitrarily combined (not shown). For example, it is also possible to replace the hole 39 in the first or second embodiment with a large window 58 on the side as shown in FIGS. In the third embodiment, the hole 60 shown in FIGS. 8 and 10 may be changed to a circular shape and used in combination with the rod-shaped portions of the lower end plugs 11 and 12 having a normal circular cross section. Further, in the third embodiment, instead of allowing the filter 56 to pass through the partition plate 30 as shown in FIG. 9, the filter 56 is placed above the opening of the partition plate 30 as in the first and second embodiments. May be covered.
[0057]
Next, a fourth embodiment of the present invention will be described with reference to FIGS. In this embodiment, the filter 65 has a substantially cylindrical shape similar to that of the filter 32 in the first embodiment (FIGS. 1 to 5), but instead of being arranged above the opening of the partition plate 30, the filter 65 It is arranged so as to pass through the circular opening 66 of the plate 30 halfway.
[0058]
In this embodiment, first, the partition plate 30 is joined to each other by welding so as to be sandwiched between the network portion 7 and the nozzle portion 8. After that, the filter 65 is inserted from the inlet opening 10 of the nozzle unit 8 and attached to the partition plate 30.
[0059]
As shown in FIG. 12, a plurality of adjacent filters 65 are connected to each other in the horizontal direction by connecting rods 67 to form a plurality (in the example of FIG. 12, nine) of groups. Each of these groups is of a size that can be inserted through the inlet opening 10 of the nozzle section 8, and for example, is basically of three rows and three columns as shown in FIG.
[0060]
As shown in FIG. 13, a groove 68 into which the connecting rod 67 can be fitted is formed on the lower surface of the partition plate 30. Further, two convex portions 69 are formed so as to sandwich the groove 68 so as to form the groove 68. The grooves 68 may be formed at positions corresponding to all the connecting rods 67. However, as long as each group of the filters 65 can be held, as shown in FIG. May be reduced.
[0061]
In this embodiment, parts other than the lower tie plate filter 65 can be assembled in advance, and the filter 65 can be inserted and assembled later. Further, at the time of refueling or the like, it is also possible to remove the filter 65 capturing foreign matter and replace it with a new filter.
[0062]
Further, in this embodiment, a plurality of filters 65 are previously connected to a plurality of groups by connecting rods 67, and these groups are inserted through the inlet opening 10 of the nozzle unit 8 and attached to the partition plate 30. Therefore, as compared with the case where each filter 65 is individually attached to the partition plate 30, the work of attaching the filter 65 can be saved. Here, the operation of connecting the plurality of filters 65 by the connecting rods 67 is relatively easy because it can be performed in a wide place, and automation is relatively easy. On the other hand, the operation of attaching the filter 65 to the partition plate 30 is performed. Is a relatively difficult operation since it is performed through the inlet opening 10 of the nozzle portion 8.
[0063]
As a modified example of the fourth embodiment, each filter 65 can be individually attached to the partition plate 30 without connecting the plurality of filters 65 with the connecting rod 67 (not shown). . In this case, instead of fitting the connecting rod 67 into the groove 68 of the partition plate 30, it is necessary to provide the partition plate 30 with unevenness (not shown) to which each filter 65 can be individually attached.
[0064]
Further, as a modified example of the fourth embodiment, it is possible to integrally cast, for example, the network part 7, the partition plate 30, and the nozzle part 8 without welding them together. That is, parts other than the lower tie plate filter 65 are assembled in advance, and the filter 65 is inserted and assembled later. In this way, the process of assembling the parts other than the lower tie plate filter 65 can be the same as the conventional process.
In the assembling method of the fourth embodiment, the filter does not necessarily have to be cylindrical, and may be applied to filters having other shapes shown in FIGS. 6 to 9.
[0065]
Next, a fifth embodiment of the present invention will be described with reference to FIGS. In this embodiment, one lower tie plate is shown as a combination of various filters. That is, the filter 32 according to the first embodiment is included, and other filters are also included.
[0066]
As shown in FIG. 15, the lower end plug 72 includes a bar-shaped portion provided with a vertical hole 73. The lower end of the vertical hole 73 is located below the partition plate 30 and opens downward. A horizontal hole 74 is connected to the upper end of the vertical hole 73, and the horizontal hole 74 opens laterally above the partition plate 30. A cylindrical filter 75 is arranged so as to surround the outside of the rod portion of the lower end plug 72. The cylindrical filter 75 is substantially the same as the filter 32 in the first embodiment, and the lower end 82 is open and the upper end 83 is closed. Further, a plurality of holes 39 are provided above the side partition plate 30.
[0067]
The coolant 15 enters the vertical hole 73 of the rod as well as the annular portion between the inner surface of the cylindrical filter 75 and the outer surface of the rod of the lower end plug 72 to form an upward flow. Any of those flows will change the direction of the flow from the ascending direction to the horizontal direction, where foreign matter in the coolant can be captured. Since the area of the flow path can be increased as compared with the case where there is no flow path in the rod portion of the lower end plug, the pressure loss can be reduced.
[0068]
As shown in FIG. 14, the perforated lower end plug 72 may be arranged independently, that is, without the filter 75.
As shown in FIG. 16, the lower end plug 77 has a bar-shaped portion that is shorter and has a lower end located above the partition plate 30. The lower end plug 77 has a vertical hole 78 having an opening at the lower end, and a vertical hole 78. A lateral hole 79 connected to the upper end of the opening 78 and opening horizontally is formed. Below this lower end plug 77, a frusto-conical filter 80 is arranged. The filter 80 is attached to the partition plate 30 through the partition plate 30 halfway, and the lower end 85 is open and the upper end 86 is closed. Further, a plurality of holes 39 are provided above the side partition plate 30. There is a gap between the lower end of the rod-shaped portion of the lower end plug 77 and the upper end of the filter 80.
[0069]
Further, as shown in FIG. 14, the filter 88 may be disposed on the partition plate 30 at a position not interfering with the lower end plug. The filter 88 has a cylindrical shape having a circular or square cross section, and is attached to the partition plate 30 so as to penetrate the partition plate 30 halfway, similarly to the filter 80. The lower end is open and the upper end is closed. On the side surface, a relatively large horizontally long window 89 is provided. By combining the filter functions of various shapes in this way, it is possible to cope with foreign substances of various shapes, and to reduce the possibility of occurrence of blockage of the flow path.
[0070]
Next, various modifications of the lower end plug 72 and the filter 75 in the fifth embodiment shown in FIG. 15 will be described with reference to FIGS.
In the example shown in FIG. 17, the outer diameter of the rod portion of the lower end plug 92 is, for example, 7 mm, and one notch 93 having a width of 0.5 mm and a length of 2 cm in the vertical direction is provided below the lower end plug rod portion. Is provided. Above the notch 93, four notches 94 each having a width of 0.5 mm and a length of 3 mm extending obliquely upward from the side surface of the rod portion are provided.
[0071]
In the example shown in FIG. 18, the outer diameter of the rod portion of the lower end plug 96 is, for example, 7 mm, and two cuts 97 having a width of 0.5 mm and a length of 2 cm in the vertical direction are provided below the lower end plug rod portion. Is provided. The central portion 98 sandwiched between the two cuts 97 extends longer than the outer portion 99 outside the cut 97. This increases the possibility that the foreign matter is caught between the cut portions.
[0072]
In the example shown in FIG. 19, similarly to the example of FIG. 15, the outer diameter of the rod portion of the lower end plug 102 is, for example, 7 mm, and the lower end opening having a diameter of 4 mm in the vertical direction at the center of the lower end plug rod portion. Vertical hole 73 is provided. A horizontal hole 74 is connected to the upper end of the vertical hole 73, and the horizontal hole 74 opens above the upper end of the filter 75. In the example of FIG. 19, two cuts 103 having a width of 0.5 mm and a length of 2 cm are vertically inserted from the lower end of the lower end plug 102. Thus, the possibility of foreign matter in the coolant being caught in the cut 103 can be increased, and the possibility of blockage of the flow path can be reduced.
[0073]
The example shown in FIG. 20 is a modification of the example of FIG. 19, in which a plurality of horizontal through holes 106 are formed in the middle of the vertical hole 73 of the rod-shaped portion of the lower end plug 105. Thereby, the possibility that foreign matter in the coolant closes the flow path can be further reduced.
[0074]
In the example shown in FIG. 21, the outer diameter of the rod-shaped portion of the lower end plug 107 is, for example, 7 mm. A cylindrical filter 75 having a diameter of, for example, 12 mm and a length of 25 mm is disposed outside the filter, and is fixed to the partition plate 30. Four grooves 108 having a depth of 1.5 mm are formed vertically in a portion above the partition plate 30 outside the rod-shaped portion of the lower end plug 107, whereby the holes 37 in the upper surface 36 of the filter 75 are formed. A flow path is formed inside. Although the flow path itself is open upward, the flow path passing through the flow path always passes through a bent portion before and after the flow path, so that a wire-like foreign matter can be particularly captured. In addition, the possibility of channel blockage can be reduced.
[0075]
In the example shown in FIG. 22, a cylindrical filter 110 having a diameter of 12 mm and a length of 32 mm is attached to the partition plate 30. The lower end 111 of the filter 110 is 5 mm below the lower surface of the partition plate 30, and four grooves 113 having a depth of 2 mm and a length of 25 mm are provided in the side surface 112 of the filter in the vertical direction from the lower end 111. Thereby, a flow path for the flow from below the partition plate 30 is secured. An annular ring 114 having a width of 2 mm is attached to the side surface 112 of the filter so as to surround the groove 113 in the circumferential direction. Thereby, in particular, it is possible to capture wire-like foreign matter, and it is possible to reduce the possibility of blockage of the flow path.
[0076]
Various embodiments of the lower tie plate according to the present invention have been described above. Various features of each of the embodiments can be arbitrarily combined. For example, it is conceivable that the lower end plug or the cylindrical filter in FIGS. 15 to 22 has a circular flat cross-sectional shape and is replaced with a square as shown in FIGS. 8 to 10. It is also possible to arrange various filters or lower end plugs in combination in one lower tie plate.
[0077]
【The invention's effect】
As described above, by employing the lower tie plate having the partition plate to which the filter of the present invention is attached, it is possible to improve the reliability of capturing foreign matter at the core inlet.
[0078]
In addition, it is possible to capture foreign materials having various shapes such as a plate shape, a spiral spring shape (spiral shape), a wire shape (straight shape), etc., thereby improving reliability against fuel damage caused by the foreign materials, and Driving performance is improved.
[Brief description of the drawings]
FIG. 1 is a schematic elevation sectional view of a first embodiment of a lower tie plate and its periphery according to the present invention.
FIG. 2 is an enlarged vertical sectional view of a main part of the lower tie plate of FIG. 1;
FIG. 3 is a partial perspective view showing a state where only one filter of FIG. 1 is attached to a partition plate.
FIG. 4 is an elevation view showing a state where only one filter of FIG. 1 is attached to a partition plate.
FIG. 5 is a plan view showing a state where the filter of FIG. 1 is attached to a partition plate.
FIG. 6 is a schematic elevation sectional view of a lower tie plate according to a second embodiment of the present invention and its periphery.
FIG. 7 is an enlarged vertical sectional view of a main part of the lower tie plate of FIG. 6;
FIG. 8 is a perspective view of a lower tie plate according to a third embodiment of the present invention in a state before a rectangular tubular filter is attached.
FIG. 9 is an elevation view showing a state where only one filter of FIG. 8 is attached to a partition plate.
FIG. 10 is a plan view showing a state where the filter of FIG. 8 is attached to a partition plate.
FIG. 11 is a schematic elevation sectional view of a lower tie plate according to a fourth embodiment of the present invention and its periphery.
FIG. 12 is a bottom view taken along line XX of FIG. 11;
FIG. 13 is a bottom view as viewed in the direction of arrows XX in a state before the filter of FIG. 11 is attached.
FIG. 14 is a schematic elevation sectional view of a lower tie plate according to a fifth embodiment of the present invention and its periphery.
15A is an enlarged vertical sectional view of a portion Y in FIG. 14, and FIG. 15B is a bottom sectional view taken along line BB of FIG.
16A is an enlarged vertical sectional view of a portion Z in FIG. 14, and FIG. 16B is a bottom view taken along line BB of FIG.
FIG. 15 is an enlarged vertical sectional view of a part Z in FIG. 14.
17A and 17B are diagrams showing another example of the combination of the lower end plug and the filter shown in FIG. 15, wherein FIG. 17A is a vertical sectional view, and FIG. 17B is a bottom sectional view taken along line BB of FIG. FIG.
18A and 18B are diagrams showing still another example of the combination of the lower end plug and the filter shown in FIG. 15, wherein FIG. 18A is a vertical sectional view, and FIG. 18B is a bottom view taken along line BB of FIG. Sectional view.
19A and 19B are diagrams showing still another example of the combination of the lower end plug and the filter shown in FIG. 15, wherein FIG. 19A is a vertical sectional view, and FIG. 19B is a bottom view taken along line BB of FIG. Sectional view.
20 is a view showing still another example of the combination of the lower end plug and the filter shown in FIG. 15, wherein (a) is a vertical sectional view, and (b) is a bottom view taken along line BB of (a). Sectional view.
21A and 21B are diagrams showing still another example of the combination of the lower end plug and the filter shown in FIG. 15, wherein FIG. 21A is a vertical sectional view, and FIG. FIG. 3C is a cross-sectional view taken along line CC of FIG.
22 is a view showing still another example of the combination of the lower end plug and the filter shown in FIG. 15, wherein (a) is a vertical sectional view, and (b) is a view taken along line BB of (a). FIG. 3C is a cross-sectional view taken along line CC of FIG.
FIG. 23 is an entire vertical sectional view of a conventional fuel assembly.
FIG. 24 is an enlarged vertical sectional view of the lower tie plate and its periphery in FIG. 23;
FIG. 25 is a plan view showing only the partition plate of FIG. 23;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Channel box, 2 ... Fuel rod, 3 ... Water rod, 4 ... Upper tie plate, 5 ... Lower tie plate, 6 ... Spacer, 7 ... Network part, 8 ... Nozzle part, 9 ... Lower tie plate cavity, 10 ... Lower tie plate inlet opening, 11, 11a: lower end plug of fuel rod, 12: lower end plug of water rod, 13: insertion hole, 15: coolant, 17: leak hole, 20: partition plate, 21: fuel rod Through hole through which the lower end plug of the water rod passes, 22 ... through hole through which the lower end plug of the water rod passes, 24 ... small hole, 26 ... inlet hole of the water rod, 27 ... outlet hole of the water rod, 30 ... partition plate, 32 ... Cylindrical filter, 35 opening, 37 hole, 38 side surface, 39 hole, 40 boss, 41 web, 45 first frustoconical filter, 46 second frustoconical filter, 47 First Mouth, 48 ... second opening, 49 ... hole, 50 ... side surface, 51 ... top surface, 52 ... hole, 53 ... side surface, 56 ... filter, 57 ... side portion, 58 ... window, 59 ... filter top surface, 60 ... hole 65, filter, 66, opening, 67, connecting rod, 68, groove, 69, convex, 72, lower end plug, 73, vertical hole, 74, horizontal hole, 75, cylindrical filter, 77, lower end plug, 78 ... vertical hole, 79 ... horizontal hole, 80 ... filter, 82 ... lower end, 83 ... upper end, 85 ... lower end, 86 ... upper end, 88 ... filter, 89 ... window, 92 ... lower end plug, 93 ... cut, 94 ... cut, 96 ... lower end plug, 97 ... cut, 99 ... outer part, 102 ... lower end plug, 103 ... cut, 105 ... lower end plug, 106 ... through hole, 107 ... lower end plug, 108 ... groove, 110 ... cylindrical filter Reference numerals 111, bottom end, 112 side, 113 groove, 1 4 ... circle ring.

Claims

A network unit that holds a lower part of the fuel rods such that a plurality of fuel rods filled with nuclear fuel are arranged in a grid at intervals.
A nozzle portion extending downward from the periphery of the network portion to form a lower tie plate cavity below the network portion and having an inlet opening at a lower end;
A partition plate disposed substantially horizontally below the network portion in the lower tie plate cavity to partition the lower tie plate cavity up and down;
A plurality of cylindrical filters attached to the partition plate and having openings below and above the partition plate,
A lower tie plate having
A lower end plug including a downwardly extending rod portion is disposed on at least a part of the plurality of fuel rods,
The upper portions of the plurality of cylindrical filters are arranged so as to surround the rod portion, and the space between the upper portion of the cylindrical filter and the rod portion is substantially closed,
An opening of the cylindrical filter above the partition plate is provided mainly on a side surface of the cylindrical filter,
Characterized by a lower tie plate.

2. The lower tie plate according to claim 1, wherein said partition plate, said network portion, and said nozzle portion are connected to each other after said tubular filter is attached to said partition plate in advance. Characteristic lower tie plate.

2. The lower tie plate according to claim 1, wherein said partition plate is inserted through said inlet opening of said nozzle portion into a pre-formed so that said partition plate is disposed between said network portion and said nozzle portion. A lower tie plate, wherein the cylindrical filter is attached.

In the lower tie plate according to claim 3, there are a plurality of connecting rods for connecting the plurality of tubular filters to each other to form a group of a plurality of tubular filters, and on a lower surface of the partition plate, A lower tie plate, comprising an engaging portion to which the connecting rod can be attached and detached.

The lower tie plate according to any one of claims 1 to 4, wherein the tubular filter has a cylindrical shape.

5. The lower tie plate according to claim 1, wherein the plurality of fuel rods are arranged in a square lattice shape, and the tubular filter has a square tubular shape arranged in the direction of the square lattice. There is a lower tie plate.

The lower tie plate according to any one of claims 1 to 4, wherein the cylindrical filter (1) has a tapered shape and a divergent shape (2).

The lower tie plate according to any one of claims 1 to 7, wherein an opening provided on a side surface of the tubular filter is circular.

A network unit that holds a lower part of the fuel rods such that a plurality of fuel rods filled with nuclear fuel are arranged in a grid at intervals.
A nozzle portion extending downward from the periphery of the network portion to form a lower tie plate cavity below the network portion and having an inlet opening at a lower end;
A partition plate disposed substantially horizontally below the network portion in the lower tie plate cavity to partition the lower tie plate cavity up and down;
A plurality of cylindrical filters attached to the partition plate and having openings below and above the partition plate,
A lower tie plate having
A lower end plug including a downwardly extending rod portion is disposed on at least a part of the plurality of fuel rods,
The upper portions of the plurality of cylindrical filters are arranged so as to surround the rod portion, and the space between the upper portion of the cylindrical filter and the rod portion is substantially closed,
In the method of assembling the lower tie plate, wherein the opening of the cylindrical filter above the partition plate is provided mainly on the side surface of the cylindrical filter,
A first step of fixing the plurality of cylindrical filters to the partition plate;
A second step of connecting the partition plates to each other so as to be sandwiched between the network section and the nozzle section after the first step;
A method of assembling a lower tie plate.

A network unit that holds a lower part of the fuel rods such that a plurality of fuel rods filled with nuclear fuel are arranged in a grid at intervals.
A nozzle portion extending downward from the periphery of the network portion to form a lower tie plate cavity below the network portion and having an inlet opening at a lower end;
A partition plate disposed substantially horizontally below the network portion in the lower tie plate cavity to partition the lower tie plate cavity up and down;
A plurality of cylindrical filters attached to the partition plate and having openings below and above the partition plate,
A lower tie plate having
A lower end plug including a downwardly extending rod portion is disposed on at least a part of the plurality of fuel rods,
The upper portions of the plurality of cylindrical filters are arranged so as to surround the rod portion, and the space between the upper portion of the cylindrical filter and the rod portion is substantially closed,
In the method of assembling the lower tie plate, wherein the opening of the cylindrical filter above the partition plate is provided mainly on the side surface of the cylindrical filter,
A first step of forming the partition plate so as to be disposed between the network section and the nozzle section;
After the first step, a second step of inserting the cylindrical filter from the inlet opening of the nozzle portion and attaching the filter to the partition plate;
A method of assembling a lower tie plate.

The method for assembling a lower tie plate according to claim 10, wherein a plurality of the cylindrical filters are connected to each other within a range that can be inserted from the inlet opening of the nozzle portion before the second step. A method of assembling a lower tie plate, further comprising a third step of previously forming a plurality of cylindrical filter groups.

The method of assembling a lower tie plate according to claim 10, wherein the lower surface of the partition plate is provided with irregularities, and the second step is configured such that the cylindrical filter is provided on the lower surface of the partition plate. A method of assembling the lower tie plate.

A plurality of fuel rods filled with nuclear fuel, at least one water rod through which a coolant passes, an upper tie plate holding upper portions of the fuel rods and the water rods, and a lower portion of the fuel rods and the water rods; And a lower tie plate to retain;
The lower tie plate is
A network section that holds the lower portions of the fuel rods and water rods such that the fuel rods and water rods are arranged in a grid at intervals.
A nozzle portion extending downward from the periphery of the network portion to form a lower tie plate cavity below the network portion and having an inlet opening at a lower end;
A partition plate disposed substantially horizontally below the network portion in the lower tie plate cavity to partition the lower tie plate cavity up and down;
A plurality of cylindrical filters attached to the partition plate and having openings below and above the partition plate,
Has,
A lower end plug including a rod portion extending downward is attached to a lower portion of at least a part of the fuel rod and the water rod,
The upper part of the plurality of cylindrical filters is arranged so as to surround the rod part of the lower end plug, and the space between the upper part of the cylindrical filter and the rod part of the lower end plug is substantially closed,
An opening of the cylindrical filter above the partition plate is provided mainly on a side surface of the cylindrical filter,
A fuel assembly characterized by the following.

The fuel assembly according to claim 13, wherein a lower end plug channel that is a coolant channel is formed inside at least one of the lower end plugs, and an entrance of the lower end plug channel is: The fuel, characterized in that it is open below and below the partition member, and the outlet of the lower end plug flow path is above the tubular filter and opens horizontally. Aggregation.

The fuel assembly according to claim 13, wherein at least one notch extending upward from at least one lower end of the lower end plug is formed.

A plurality of fuel rods filled with nuclear fuel, at least one water rod through which a coolant passes, an upper tie plate holding upper portions of the fuel rods and the water rods, and a lower portion of the fuel rods and the water rods; And a lower tie plate to retain;
The lower tie plate is
A network section that holds the lower portions of the fuel rods and water rods such that the fuel rods and water rods are arranged in a grid at intervals.
A nozzle portion extending downward from the periphery of the network portion to form a lower tie plate cavity below the network portion and having an inlet opening at a lower end;
A partition plate disposed substantially horizontally below the network portion in the lower tie plate cavity to partition the lower tie plate cavity up and down;
A plurality of cylindrical filters attached to the partition plate at a position directly below the fuel rod and the water rod, and having openings below and above the partition plate;
Has,
An opening of the cylindrical filter above the partition plate is provided mainly on a side surface of the cylindrical filter,
A lower end plug including a rod portion extending downward is attached to a lower portion of at least a part of the fuel rod and the water rod, and a lower end of the rod portion is located at a position higher than an upper end of the cylindrical filter. A lower end plug channel having a downwardly directed inlet opening at the lower end of the rod-shaped portion and having a horizontally oriented outlet opening above the lower end plug passage is formed in the lower end plug,
A fuel assembly characterized by the following.