JP2005049256A - Fuel assembly for boiling water reactor - Google Patents

Fuel assembly for boiling water reactor Download PDF

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JP2005049256A
JP2005049256A JP2003282419A JP2003282419A JP2005049256A JP 2005049256 A JP2005049256 A JP 2005049256A JP 2003282419 A JP2003282419 A JP 2003282419A JP 2003282419 A JP2003282419 A JP 2003282419A JP 2005049256 A JP2005049256 A JP 2005049256A
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spacer
fuel assembly
flow
spacers
pressure loss
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Masahiko Sanbe
昌彦 三部
Hiroyori Isaka
浩順 井坂
Riichiro Suzuki
理一郎 鈴木
Yuji Nishino
祐治 西野
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Nuclear Fuel Industries Ltd
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Nuclear Fuel Industries Ltd
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    • 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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Abstract

<P>PROBLEM TO BE SOLVED: To obtain a boiling water reactor having an enhanced heating margin without increase in pressure loss. <P>SOLUTION: In a fuel assembly for a boiling water reactor loaded with a bundle of a plurality of rod elements including fuel rods arranged parallelly between an upper tie plate and a lower tie plate by using a plurality of spacers retaining them apart from each other, the lowest and the highest spacers are not provided with a mixing vane and a flow tab, substantially, and the other spacers are provided with the mixing vane and the flow tab. Further, the fuel assembly having the second lowest spacer which is not provided with the mixing vane and the flow tab, substantially, is also disclosed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

本発明は、ミキシングベーン及びフロータブ付きスペーサを複数装着した沸騰水型原子炉用燃料集合体に関し、特に、圧力損失の増大を伴わずに熱的余裕（限界出力特性）の改善を可能にするために、最下位のスペーサもしくは最下位及び下端から２番目のスペーサ、並びに最上位のスペーサのミキシングベーン実質全部を削除し、かつ前記スペーサのフロータブの実質全部を削除したことを特徴とするスペーサを具備した燃料集合体に関するものである。   The present invention relates to a fuel assembly for a boiling water reactor equipped with a plurality of mixing vanes and spacers with flow tabs, and more particularly to enable improvement of thermal margin (limit power characteristics) without increasing pressure loss. And the lowermost spacer or the second spacer from the lowermost and lowermost ends, and substantially all of the mixing vanes of the uppermost spacer are deleted, and substantially all of the flow tabs of the spacer are deleted. It relates to the fuel assembly.

沸騰水型原子炉（以下、ＢＷＲと略す）に装荷される燃料集合体は、図１２に示すように燃料棒Ａで代表される棒状燃料要素を正方配列し、それらの上下端は端栓を介して上下の支持板（タイプレート）２、３に装着され、中間高さ位置の複数箇所にはスペーサ５を所定間隔に保持したものが一般的である。   A fuel assembly loaded in a boiling water reactor (hereinafter abbreviated as BWR) has rod-like fuel elements represented by fuel rod A squarely arranged as shown in FIG. In general, the upper and lower support plates (tie plates) 2 and 3 are attached to each other, and the spacers 5 are held at predetermined intervals at a plurality of intermediate height positions.

このような燃料集合体１は、炉心Ｒにおいては各燃料棒Ａを除熱する冷却水確保のため、ジルカロイ製の角筒状のチャンネルボックス４内に収められて炉心構造部の受座に所要数装荷され、原子炉運転中は受座の入口オリフィスからチャンネルボックス４内及びウォータチャンネルＷ内に冷却水を送り込んで各燃料集合体の燃料棒の間を上向きに流れるようにし、制御棒Ｃで制御すると共に燃料棒の反応熱で冷却水を沸騰させて熱を外部に取り出すと共に燃料集合体の除熱を行うようにしている。   Such a fuel assembly 1 is housed in a rectangular tubular channel box 4 made of Zircaloy and required for seating of the core structure in order to secure cooling water for removing heat from each fuel rod A in the core R. During the operation of the reactor, cooling water is fed into the channel box 4 and the water channel W from the inlet orifice of the seat so that it flows upward between the fuel rods of each fuel assembly. In addition to controlling, the cooling water is boiled by the reaction heat of the fuel rods to extract the heat to the outside and to remove heat from the fuel assembly.

ＢＷＲは炉内で水蒸気を発生させる直接サイクル方式であるため、炉心内で沸騰を許容している。したがって、燃料の冷却は、液相・蒸気（ボイド）の二相流の条件下で行われ、ボイド率の高い燃料集合体上部の冷却水の流動様式は、図１３に示すように膜状の液相（液膜）ａ１がチャンネルボックス４の内壁面と燃料棒Ａの外周面でそれぞれ連続した環状流れが、また、チャンネルボックスと燃料棒との間及び燃料棒同士の間には液滴ａ２を伴う蒸気相ｂが流れるいわゆる環状流が形成され、燃料棒の外周面の前記液膜ａ１が燃料棒の冷却に重要な役割を果たす。   Since BWR is a direct cycle system that generates water vapor in the furnace, boiling is allowed in the core. Therefore, the cooling of the fuel is performed under the condition of a two-phase flow of liquid phase and vapor (void), and the flow pattern of the cooling water above the fuel assembly having a high void ratio is a film-like shape as shown in FIG. An annular flow in which the liquid phase (liquid film) a1 continues on the inner wall surface of the channel box 4 and the outer peripheral surface of the fuel rod A, and the droplet a2 between the channel box and the fuel rod and between the fuel rods. A so-called annular flow is formed in which the vapor phase b flows along with the fuel film, and the liquid film a1 on the outer peripheral surface of the fuel rod plays an important role in cooling the fuel rod.

しかしながら、例えば過出力状態等の何らかの原因で燃料集合体が熱的に厳しい状態におかれ、いわゆる核沸騰状態から膜沸騰状態への遷移（沸騰遷移）が生じると、図１４に示すように燃料棒Ａの外周面の液膜ａ１が消失して除熱効果が急激に悪化するため、燃料棒Ａの液膜消失領域における温度が急激に上昇し、ついにはその部分でバーンアウトを生ずることとなる。ＢＷＲに特徴的な液膜の消失に伴うバーンアウトを特にドライアウトと呼び、ドライアウトの生ずる燃料集合体全体の熱負荷を限界出力と呼んでいる。   However, if the fuel assembly is placed in a thermally severe state for some reason, such as an overpower state, and a transition from a so-called nucleate boiling state to a film boiling state (boiling transition) occurs, the fuel as shown in FIG. Since the liquid film a1 on the outer peripheral surface of the rod A disappears and the heat removal effect deteriorates rapidly, the temperature in the liquid film disappearing region of the fuel rod A suddenly rises, and eventually burnout occurs at that portion. Become. The burnout associated with the disappearance of the liquid film characteristic of BWR is particularly called dryout, and the thermal load of the entire fuel assembly where dryout occurs is called the limit output.

限界出力を向上する方策として種々のスペーサが提案されており、その代表として混合羽根、すなわちミキシングベーン付きスペーサが特許文献１に、フロータブ付きスペーサが特許文献２に開示されている。図１５にミキシングベーン付きスペーサを示す。図１６にフロータブ付きスペーサを示す。   Various spacers have been proposed as measures for improving the limit output, and as typical examples, a mixing blade, that is, a spacer with a mixing vane is disclosed in Patent Document 1, and a spacer with a flow tab is disclosed in Patent Document 2. FIG. 15 shows a spacer with a mixing vane. FIG. 16 shows a spacer with a flow tab.

図１５に示すミキシングベーン５１は、燃料棒Ａを抑圧、支持するスプリング５２を具備した外側板及び格子板５３と、燃料棒Ａで囲まれたサブチャンネル流路のおよそ中心位置に相当するこの格子板５３の交点を中心として突設された羽根５４とで構成される。ミキシングベーン５１はスペーサ５の上面、すなわち冷却材流れ方向の下流側に取り付けられる。これらのミキシングベーン５１はサブチャンネル内で冷却材に遠心力を付加して旋回流を引き起こし、重量の重い液滴を選択的に燃料棒に付着させ、軽い蒸気はサブチャンネル中央付近に偏流させる効果がある。このことによってスペーサ下流側の燃料棒Ａの液膜が厚くなり、液膜の消失に至るまでの熱負荷が大きくなるため、限界出力は増大する。   The mixing vane 51 shown in FIG. 15 has an outer plate and a lattice plate 53 having springs 52 for suppressing and supporting the fuel rod A, and this lattice corresponding to the approximate center position of the subchannel flow path surrounded by the fuel rod A. It is comprised with the blade | wing 54 protruded centering | focusing on the intersection of the board 53. FIG. The mixing vane 51 is attached to the upper surface of the spacer 5, that is, the downstream side in the coolant flow direction. These mixing vanes 51 add a centrifugal force to the coolant in the subchannel to cause a swirling flow, selectively cause heavy droplets to adhere to the fuel rods, and light steam drifts near the center of the subchannel. There is. As a result, the liquid film of the fuel rod A on the downstream side of the spacer becomes thick, and the thermal load until the liquid film disappears increases, so that the limit output increases.

一方、図１６に示すフロータブ６１は、スペーサ５の外側板６２もしくは格子板６３の上面部から内装された燃料棒Ａ側へ向け傾倒曲成され、かつ当該燃料棒間配置で所定距離だけ離間突設される。これらのフロータブ６１は最外周燃料棒Ａとチャンネルボックス４、もしくは最内層燃料棒ＡとウォータチャンネルＷの間隙を上向きに流送される蒸気重量率（クォリティ）の低い冷却材を内側隣接燃料棒に変向流導させる効果がある。このことによってスペーサ下流側の特に最外周燃料棒Ａ、もしくは最内層燃料棒Ａの液膜が厚くなり、限界出力は増大する。   On the other hand, the flow tab 61 shown in FIG. 16 is bent and inclined from the upper surface of the outer plate 62 or the lattice plate 63 of the spacer 5 toward the fuel rod A, and is spaced apart by a predetermined distance in the arrangement between the fuel rods. Established. These flow tabs 61 are provided with coolant having a low vapor weight ratio (quality), which is sent upward through the gap between the outermost fuel rod A and the channel box 4 or between the innermost fuel rod A and the water channel W, on the inner adjacent fuel rod. This has the effect of turning the current. As a result, the liquid film of the outermost fuel rod A or the innermost fuel rod A on the downstream side of the spacer becomes thick, and the limit output increases.

ところで、ミキシングベーン５１及びフロータブ６１は上向きに流送される冷却材を強制的に偏流させるため、限界出力向上の効果を有する反面、冷却材の流動抵抗及びエネルギ損失の拡大に伴い圧力損失を増大させる性質を持つ。すなわち、一般的にミキシングベーン及びフロータブは、これら冷却材と接触面積が大きいほど、冷却材の偏流効果が大きいため除熱性能が向上し限界出力は向上するが、逆に局所的な圧力損失（スペーサ圧損）は増大する傾向にある。   By the way, the mixing vane 51 and the flow tab 61 forcibly drift the coolant flowing upward, so that it has the effect of improving the limit output, but the pressure loss increases as the flow resistance and energy loss of the coolant increase. It has a nature to let you. That is, in general, the mixing vane and the flow tab have a larger drifting effect of the coolant as the contact area with the coolant is larger, so that the heat removal performance is improved and the limit output is improved, but conversely the local pressure loss ( (Spacer pressure loss) tends to increase.

このようにミキシングベーン及びフロータブ付きスペーサを具備した燃料集合体では、燃料集合体の熱的余裕は向上するが、同時に圧力損失も増大してしまう課題があった。この問題点を解決する手段として、後述するように熱的余裕に与える影響の少ない最下位及び最上位のスペーサにミキシングベーンを設けず、圧力損失の低減を図った燃料集合体が特許文献３に開示されている。   As described above, in the fuel assembly including the mixing vane and the spacer with the flow tab, the thermal margin of the fuel assembly is improved, but at the same time, the pressure loss is increased. As a means for solving this problem, Japanese Patent Application Laid-Open No. H10-228867 discloses a fuel assembly that reduces pressure loss without providing mixing vanes in the lowermost and uppermost spacers that have little influence on the thermal margin as will be described later. It is disclosed.

一方、圧力損失の低減を図りながら、限界出力の向上に寄与するスペーサとして図１７に示された管状フェルール７０を備えたスペーサ及び図１８に示された管状フェルールの間隙の下流部（上端）に旋回ベーンとしてねじり翼８０を備えたスペーサが提案されている（例えば、特許文献４及び特許文献５参照）。   On the other hand, the spacer having the tubular ferrule 70 shown in FIG. 17 as a spacer contributing to the improvement of the limit output while reducing the pressure loss, and the downstream portion (upper end) of the gap of the tubular ferrule shown in FIG. A spacer having a torsional blade 80 as a turning vane has been proposed (see, for example, Patent Document 4 and Patent Document 5).

特許公報３２６７９６７Patent Publication 3267967 特開２００１−１８３４８５JP 2001-183485 A 特開２００１−３１８１８２JP 2001-318182 A 特許３０３８２６６Patent 3038266 特許３１９５１０１Patent 3195101

しかしながら、発明者の知見によれば、スペーサ圧損に占めるミキシングベーン及びフロータブのスペーサ圧損全体に占める影響の割合は標準的な例ではそれぞれ約０．１５、約０．２であり、前記特許文献３のようなミキシングベーンの除去だけでは圧力損失低減の観点から十分な対策とは云えなかった。また、前記特許文献３ではミキシングベーンのみ削除するため、フロータブの突設される燃料集合体周辺部に比べて中央部の流動抵抗が少なくなり、当該スペーサにおいて冷却材が相対的に燃料集合体中央に多く集まるような流量再配分が生じ、冷却材流れ方向下流側での燃料集合体内の流量不均一分布の発生を招く可能性があった。   However, according to the inventor's knowledge, the ratio of the influence of the mixing vane and the flow tab in the total spacer pressure loss in the spacer pressure loss is about 0.15 and about 0.2 in the standard example, respectively. The removal of the mixing vane alone is not a sufficient measure from the viewpoint of reducing the pressure loss. In addition, since only the mixing vane is deleted in Patent Document 3, the flow resistance in the central portion is smaller than that in the peripheral portion of the fuel assembly on which the flow tab protrudes, and the coolant is relatively located in the center of the fuel assembly in the spacer. Therefore, there is a possibility that the flow rate redistribution is concentrated in the fuel assembly, resulting in the occurrence of a non-uniform flow rate distribution in the fuel assembly on the downstream side in the coolant flow direction.

本発明は、以上の燃料集合体内の冷却材熱流動特性を考慮した上で、熱的余裕に与える影響の少ない区間にあるスペーサのミキシングベーンの実質全部及び前記スペーサのフロータブの実質全部を除去することにより圧力損失低減を徹底し、この圧力損失低減を補償すべく上記以外の区間にあるスペーサのミキシングベーン及びフロータブの大きさをそれらが軸方向で一様とした場合に比べて大きくし、このことにより圧力損失の増加がなく、かつ熱的余裕の向上した燃料集合体を得ることを目的とする。   The present invention removes substantially all of the mixing vanes of the spacer and substantially all of the flow tabs of the spacer in the section having a small influence on the thermal margin in consideration of the above-described coolant heat flow characteristics in the fuel assembly. In order to compensate for this pressure loss reduction, the spacer mixing vanes and flow tabs in the sections other than the above are made larger than those in the case where they are uniform in the axial direction. Accordingly, an object of the present invention is to obtain a fuel assembly having no increase in pressure loss and an improved thermal margin.

請求項１に記載された発明に係るＢＷＲ用燃料集合体は、上部タイプレートと下部タイプレートとの間に平行配列された燃料棒を含む複数の棒状要素を、これら棒状要素を相互に間隔を開けて保持する複数のスペーサによって、バンドル状に装荷した沸騰水型原子炉用燃料集合体において、
最下位及び最上位のスペーサにミキシングベーンとフロータブとを実質的に具備せず、その他のスペーサにミキシングベーン及びフロータブを具備したことを特徴とするものである。 The fuel assembly for a BWR according to the first aspect of the present invention includes a plurality of rod-like elements including fuel rods arranged in parallel between an upper tie plate and a lower tie plate, and the rod-like elements are spaced from each other. In a boiling water reactor fuel assembly loaded in a bundle by a plurality of spacers that are opened and held,
The lowermost and uppermost spacers are substantially not provided with mixing vanes and flow tabs, and the other spacers are provided with mixing vanes and flow tabs.

請求項２に記載された発明に係るＢＷＲ用燃料集合体は、請求項１に記載の最下位から２番目のスペーサについてもミキシングベーンとフロータブとを実質的に具備しないことを特徴とするものである。   The fuel assembly for a BWR according to the invention described in claim 2 is characterized in that the second lowest-most spacer according to claim 1 does not substantially include a mixing vane and a flow tab. is there.

請求項３に記載された発明に係るＢＷＲ用燃料集合体は、請求項１又は２に記載のミキシングベーンとフロータブとを実質的に具備しないスペーサに、１面あたり２個程度のガイドインタブを具備したことを特徴とするものである。   A fuel assembly for a BWR according to the invention described in claim 3 is provided with about two guide-in tabs per surface on a spacer that does not substantially include the mixing vane and the flow tab according to claim 1 or 2. It is characterized by that.

本発明は以上説明した通り、圧力損失の増加がなく、かつ熱的余裕の向上した燃料集合体を得ることができるという効果がある。   As described above, the present invention has an effect that there is no increase in pressure loss and a fuel assembly with improved thermal margin can be obtained.

図１は一般的な燃料棒表面の液膜厚さの軸方向変化を示す線図である。図に示す通り、ボイド率の低い軸方向下部では液膜は厚く、上側（下流）側に行くに従ってボイド率が大きくなるため、液膜厚さは小さくなる。スペーサの直上ではミキシングベーン及びフロータブによる冷却材の偏流効果のため液膜厚さが回復するが、通常最上部もしくはそれより一段下側のスペーサの直下でドライアウトが発生する。最上部のスペーサの上側（下流）側は、ボイド率が高いにもかかわらず熱流束が低いため、熱的余裕は大きくなる。   FIG. 1 is a diagram showing an axial change in the liquid film thickness on the surface of a general fuel rod. As shown in the figure, the liquid film is thick at the lower axial portion where the void ratio is low, and the void ratio increases toward the upper (downstream) side, so the liquid film thickness decreases. The liquid film thickness is recovered immediately above the spacer due to the drift effect of the coolant due to the mixing vane and the flow tab, but usually dryout occurs immediately below the uppermost spacer or one step below the spacer. The upper (downstream) side of the uppermost spacer has a low thermal flux despite a high void fraction, so that the thermal margin increases.

図２は燃料集合体の一般的な圧力損失の軸方向分布を示す線図である。図に示す通り、圧力損失はスペーサ圧力損失を含む局所圧力損失、摩擦圧力損失、加速圧力損失、静水頭からなるが、局所圧力損失及び摩擦圧力損失はボイド率が大きくなると二相圧損倍率が急増するため、軸方向の長さに対して下に凸の曲線になる。スペーサ位置ではスペーサの局所圧力損失のため圧力損失が大きくなり、その増分はボイド率が大きくなる、すなわち上側（下流）側に行くに従って拡大する。標準的な設計では全スペーサ圧損の集合体圧力損失に占める割合は約０．３である。   FIG. 2 is a diagram showing a general pressure loss axial distribution of the fuel assembly. As shown in the figure, the pressure loss consists of local pressure loss including spacer pressure loss, friction pressure loss, acceleration pressure loss, and hydrostatic head, but local pressure loss and friction pressure loss increase rapidly when the void fraction increases. Therefore, it becomes a downwardly convex curve with respect to the length in the axial direction. At the spacer position, the pressure loss increases due to the local pressure loss of the spacer, and the increment increases as the void ratio increases, that is, toward the upper (downstream) side. In a standard design, the ratio of total spacer pressure loss to aggregate pressure loss is about 0.3.

従って、本発明では、沸騰水型原子炉用燃料集合体において、最下位及び最上位のスペーサにミキシングベーンとフロータブとを実質的に具備せず、その他のスペーサにミキシングベーン及びフロータブを具備したものであるため、圧力損失の増加がなく、かつ熱的余裕の向上した燃料集合体を得ることができる。具体的には、最下位及び下端から２番目のスペーサ並びに最上位のスペーサ以外のスペーサのミキシングベーン及びフロータブの大きさを前記標準ケースのスペーサのミキシングベーン及びフロータブより大きくすることにより、燃料集合体の全圧力損失を標準ケースの圧力損失と同等にすることができる。   Therefore, in the present invention, in the boiling water reactor fuel assembly, the lowermost and uppermost spacers are substantially not provided with mixing vanes and flow tabs, and the other spacers are provided with mixing vanes and flow tabs. Therefore, it is possible to obtain a fuel assembly with no increase in pressure loss and improved thermal margin. Specifically, the size of the mixing vanes and flow tabs of the spacers other than the lowermost and lowermost spacers and the spacers other than the uppermost spacer is made larger than the mixing vanes and flow tabs of the spacers of the standard case, thereby The total pressure loss can be made equal to the pressure loss of the standard case.

尚、本発明において、最下位及び最上位のスペーサにミキシングベーンとフロータブとを実質的に具備しないこととは、具体的には、上向きに流送される冷却材を強制的に偏流させるミキシングベーンとフロータブとを具備しないことであり、冷却材を強制的に偏流させる目的でない限り、ミキシングベーン様部材及びフロータブ様部材を設けても良い。例えば、燃料集合体にチャンネルボックスを装着する際にチャンネルボックスとスペーサが衝突しないようにガイドの役割を担わせるタブ部材は本発明における具備しないものとは相違する。   In the present invention, the fact that the lowermost and uppermost spacers are substantially not provided with a mixing vane and a flow tab specifically means that the mixing vane forcibly drifts the coolant that flows upward. In other words, a mixing vane-like member and a flow tab-like member may be provided unless the purpose is to forcibly drift the coolant. For example, a tab member that plays the role of a guide so that the channel box and the spacer do not collide when the channel box is mounted on the fuel assembly is different from that not provided in the present invention.

図３は本発明のＢＷＲ型燃料集合体の一実施例の構成を示す説明図である。本発明では、ボイド率が低く熱的裕度の大きな区間にある最下位のスペーサもしくは最下位及び下端から２番目のスペーサ、並びにボイド率が高いにもかかわらず熱流束が低いため熱定余裕に与える影響の少ない区間にある最上部のスペーサのミキシングベーンの全部及び前記区間にあるスペーサのフロータブの実質全部を削除することによってスペーサ圧損を低減し、低減した圧力損失を補償するため、前記区間以外にあるスペーサのミキシングベーン及びフロータブの大きさを、燃料集合体に装備される全スペーサのミキシングベーン及びフロータブが一律にそれぞれ同じ大きさとした標準ケースに比べて大きくすることによって、燃料集合体の圧力損失の増大を伴わずに熱的余裕を向上させることができる。   FIG. 3 is an explanatory view showing the configuration of one embodiment of the BWR type fuel assembly of the present invention. In the present invention, the lowest spacer in the section having a low void ratio and a large thermal margin or the second spacer from the lowest and lower ends, and the heat flux is low despite the high void ratio, so that the thermal constant margin is increased. In order to reduce spacer pressure loss and compensate for the reduced pressure loss by removing all of the mixing vanes of the uppermost spacer in the section with little influence and substantially all of the flow tabs of the spacer in the section other than the above section The pressure of the fuel assembly is increased by increasing the size of the mixing vanes and flow tabs of the spacers in the standard case where the mixing vanes and flow tabs of all the spacers installed in the fuel assembly are uniformly the same size. The thermal margin can be improved without increasing the loss.

なお、フロータブについては圧力損失低減の観点から全数削除が好ましいが、燃料集合体１にチャンネルボックス４を装着する際にチャンネルボックスとスペーサが衝突しないようにガイドの役割を担わせることが重要である。図４は本発明の圧力損失低減用スペーサでのフロータブの装着状態の一実施例を示す説明図である。図４に示すようにスペーサ１面あたり２個程度のフロータブ４１をガイドインタブとして残すことが現実的である。これによりチャンネルボックス４の燃料集合体１への装着時に想定されるスペーサ破損トラブルを回避することができる。ガイドインタブの大きさは前記標準ケースのスペーサのフロータブより大きくても小さくても構わない。   Although it is preferable to delete all the flow tabs from the viewpoint of reducing pressure loss, it is important to play a role of a guide so that the channel box and the spacer do not collide when the channel box 4 is attached to the fuel assembly 1. . FIG. 4 is an explanatory view showing an embodiment of a mounting state of the flow tab in the pressure loss reducing spacer of the present invention. As shown in FIG. 4, it is practical to leave about two flow tabs 41 per spacer surface as guide-in tabs. As a result, it is possible to avoid a spacer damage trouble assumed when the channel box 4 is attached to the fuel assembly 1. The size of the guide in tab may be larger or smaller than the flow tab of the spacer of the standard case.

図５は本発明の一実施例として７枚のスペーサを具備した燃料集合体の構成を示す説明図である。また、図６は本発明の別の実施例として８枚のスペーサを具備した燃料集合体の構成を示す説明図である。図５，図６での添え字は下端からの番号を示す。
ａ）ＥＧ１，ＭＦ２，ＭＦ３，ＭＦ４，ＦＭ５，ＭＦ６，ＥＧ７ 図５ａ
ｂ）ＥＧ１，ＥＧ２，ＭＦ３，ＭＦ４，ＦＭ５，ＭＦ６，ＥＧ７ 図５ｂ
ｃ）ＥＧ１，ＭＦ２，ＭＦ３，ＭＦ４，ＦＭ５，ＭＦ６，ＭＦ７，ＥＧ８ 図６ａ
ｄ）ＥＧ１，ＥＧ２，ＭＦ３，ＭＦ４，ＦＭ５，ＭＦ６，ＭＦ７，ＥＧ８ 図６ｂ
ＥＧ：ミキシングベーン全数削除、フロータブ実質全数削除したスペーサ
ＭＦ：ミキシングベーン及びフロータブを備えたスペーサ FIG. 5 is an explanatory view showing the structure of a fuel assembly having seven spacers as an embodiment of the present invention. FIG. 6 is an explanatory view showing the structure of a fuel assembly having eight spacers as another embodiment of the present invention. 5 and 6 indicate numbers from the lower end.
a) EG1, MF2, MF3, MF4, FM5, MF6, EG7 FIG.
b) EG1, EG2, MF3, MF4, FM5, MF6, EG7 FIG.
c) EG1, MF2, MF3, MF4, FM5, MF6, MF7, EG8 FIG.
d) EG1, EG2, MF3, MF4, FM5, MF6, MF7, EG8 FIG.
EG: Spacer with all mixing vanes removed and all flow tabs removed MF: Spacer with mixing vanes and flow tabs

図７は本発明の燃料集合体と従来の燃料集合体との圧力損失の軸方向分布を比較した線図である。即ち、燃料集合体に装備した複数のスペーサのうち、最下位及び下端から２番目のスペーサ並びに最上位のスペーサのミキシングベーンの全部及び前記スペーサのフロータブの１面あたり２個を残して削除し、前記以外のスペーサには後記標準ケースのスペーサを備えた燃料集合体の圧力損失の軸方向変化を、燃料集合体に装備される全スペーサのミキシングベーン及びフロータブが一律にそれぞれ同じ大きさとした標準ケースのスペーサを備えた燃料集合体の圧力損失の軸方向変化と比較した。   FIG. 7 is a diagram comparing axial distributions of pressure loss between the fuel assembly of the present invention and a conventional fuel assembly. That is, among the plurality of spacers equipped in the fuel assembly, the second lowest spacer and the second spacer from the lower end, and all the mixing vanes of the uppermost spacer and two per one surface of the flow tab of the spacer are deleted, Other than the above spacers, the standard case in which the axial change of the pressure loss of the fuel assembly provided with the spacer of the standard case described later is uniformly the same in the mixing vanes and flow tabs of all the spacers equipped in the fuel assembly. The fuel assemblies with different spacers were compared with the axial change of pressure loss.

図８は本発明の燃料集合体と従来の燃料集合体との液膜厚さの軸方向変化を比較した線図である。即ち、本発明による前記２種類のスペーサを備えた燃料集合体と標準ケースの燃料集合体とについて熱的余裕に直接関連する液膜厚さの軸方向変化を比較した。図に示す通り、本発明では最下位及び下端から２番目のスペーサ並びに最上位のスペーサに低圧損型スペーサを備えているため、標準ケースに比べて圧力損失低減が実現される。一方、本発明では最上端付近の液膜厚さは若干小さくなるものの、熱的余裕に影響のない区間のスペーサのミキシングベーン及びフロータブが削除されているため、標準ケ一スと比べて熱的余裕の減少はない。   FIG. 8 is a diagram comparing axial changes in the liquid film thickness between the fuel assembly of the present invention and a conventional fuel assembly. That is, the axial change of the liquid film thickness directly related to the thermal margin was compared between the fuel assembly provided with the two types of spacers according to the present invention and the fuel assembly of the standard case. As shown in the drawing, in the present invention, the pressure loss reduction is realized compared to the standard case because the lowest spacer and the second spacer from the lower end and the uppermost spacer are provided with the low pressure loss type spacer. On the other hand, in the present invention, although the liquid film thickness near the uppermost end is slightly smaller, the mixing vanes and flow tabs of the spacers that do not affect the thermal margin are deleted, so that the thermal thickness is smaller than that of the standard case. There is no reduction in margin.

図９は本発明によるスペーサと他のスペーサとの冷却材の流量分布を比較したものであり、ａ図は計測する場所を示し、ｂ図は比較した線図である。即ち、燃料集合体の最下位位置における本発明によるスペーサ、特許文献３（特開２００１−３１８１８２）で開示されているスペーサ及び標準ケースのスペーサでの冷却材の流量分布を比較した。ｂ図に示す通り、本発明によるスペーサでの流量分布はミキシングベーンの全部及び前記スペーサのフロータブの１面あたり２個を残して削除することによって燃料集合体内の流動抵抗の分布が均一化するため、むしろ標準ケースのスペーサでの流量分布よりも一様となり、特許文献３で開示されているスペーサに対して不均一度、特に最外周燃料棒近傍の流量の偏りが改善されることが判った。   FIG. 9 compares the flow rate distribution of the coolant between the spacer according to the present invention and other spacers. FIG. 9a shows a place to be measured, and FIG. 9b is a comparative diagram. That is, the flow rate distribution of the coolant was compared between the spacer according to the present invention at the lowest position of the fuel assembly, the spacer disclosed in Patent Document 3 (Japanese Patent Laid-Open No. 2001-318182), and the spacer of the standard case. As shown in FIG. b, the flow distribution in the spacer according to the present invention is eliminated by leaving all of the mixing vanes and two per one surface of the flow tab of the spacer, thereby making the flow resistance distribution in the fuel assembly uniform. Rather, it was found that the flow distribution in the standard case spacer was more uniform, and the non-uniformity, particularly the flow rate deviation in the vicinity of the outermost fuel rod, was improved compared to the spacer disclosed in Patent Document 3. .

本発明において、最下位及び下端から２番目のスペーサ並びに最上位のスペーサの以外のスペーサのミキシングベーン及びフロータブの大きさを前記標準ケースのスペーサのミキシングベーン及びフロータブより大きくすることにより、燃料集合体の全圧力損失を標準ケースの圧力損失と同等にすることができる。図１０はこの場合の燃料集合体と従来の燃料集合体との圧力損失の軸方向分布を比較した線図である。即ち、上記ケースの圧力損失の軸方向変化を標準ケースと比較して示す。最下位及び下端から２番目のスペーサ並びに最上位のスペーサの以外のスペーサのミキシングベーン及びフロータブの大きさを大きくすることにより、圧力損失低下分が補償されていることがわかる。図１１は図１０と同様の場合の液膜厚さの軸方向変化を標準ケースと比較した線図である。最下位及び下端から２番目のスペーサ並びに最上位のスペーサの以外のスペーサのミキシングベーン及びフロータブの大きさを大きくすることにより、標準ケースに比べ、熱的余裕が改善されることがわかる。   In the present invention, the size of the mixing vanes and flow tabs of the spacers other than the lowermost and lowermost spacers and the spacers other than the uppermost spacer are made larger than the mixing vanes and flow tabs of the spacers of the standard case. The total pressure loss can be made equal to the pressure loss of the standard case. FIG. 10 is a diagram comparing the axial distribution of pressure loss between the fuel assembly in this case and the conventional fuel assembly. That is, the change in the axial direction of the pressure loss in the above case is shown in comparison with the standard case. It can be seen that the pressure loss drop is compensated for by increasing the size of the mixing vanes and flow tabs of the spacers other than the lowest spacer and the second lowest spacer and the spacer at the top. FIG. 11 is a diagram in which the change in the axial direction of the liquid film thickness in the case similar to FIG. 10 is compared with the standard case. It can be seen that the thermal margin is improved as compared with the standard case by increasing the sizes of the mixing vanes and flow tabs of the spacers other than the lowest spacer and the second lowest spacer and the uppermost spacer.

以上、本発明で云うミキシングベーンは図１５の特許文献１（特許公報３２６７９６７）の開示例、すなわち格子板の交点に設けた複数の羽根を意味するが、図１７の特許文献４（特許公報３０３８２６６）の開示例、すなわち燃料棒挿通路が形成されるよう互いに点溶接された円筒状の丸セルの上端に設けられた突起物、及び図１８の特許文献５（特許公報３１９５１０１）の開示例、すなわち前記点溶接された複数個の丸セルの間隙部上端に設けられた羽根もしくは突起物は前記ミキシングベーンと同じ熱水力的特性を有しており、本発明の範疇の中にあることは言うまでもない。   As mentioned above, the mixing vane referred to in the present invention means an example disclosed in Patent Document 1 (Patent Publication 3267967) in FIG. 15, that is, a plurality of blades provided at intersections of lattice plates. ), That is, a protrusion provided at the upper end of a cylindrical round cell spot welded to each other so that a fuel rod insertion passage is formed, and a disclosure example of Patent Document 5 (Patent Publication 3195101) in FIG. That is, the blades or projections provided at the upper ends of the gaps of the plurality of spot-welded round cells have the same thermo-hydraulic characteristics as the mixing vanes, and are within the scope of the present invention. Needless to say.

一般的な燃料棒表面の液膜厚さの軸方向変化を示す線図である。It is a diagram which shows the axial direction change of the liquid film thickness of the general fuel rod surface. 燃料集合体の一般的な圧力損失の軸方向分布を示す線図である。It is a diagram which shows the axial distribution of the general pressure loss of a fuel assembly. 本発明のＢＷＲ型燃料集合体の一実施例の構成を示す説明図である。It is explanatory drawing which shows the structure of one Example of the BWR type fuel assembly of this invention. 本発明の圧力損失低減用スペーサでのフロータブの装着状態の一実施例を示す説明図である。It is explanatory drawing which shows one Example of the mounting state of the flow tab in the spacer for pressure loss reduction of this invention. 本発明の一実施例として７枚のスペーサを具備した燃料集合体の構成を示す説明図である。It is explanatory drawing which shows the structure of the fuel assembly provided with seven spacers as one Example of this invention. 本発明の別の実施例として８枚のスペーサを具備した燃料集合体の構成を示す説明図である。It is explanatory drawing which shows the structure of the fuel assembly provided with eight spacers as another Example of this invention. 本発明の燃料集合体と従来の燃料集合体との圧力損失の軸方向分布を比較した線図である。It is the diagram which compared the axial direction distribution of the pressure loss of the fuel assembly of this invention, and the conventional fuel assembly. 本発明の燃料集合体と従来の燃料集合体との液膜厚さの軸方向変化を比較した線図である。It is the diagram which compared the axial direction change of the liquid film thickness of the fuel assembly of this invention, and the conventional fuel assembly. 本発明によるスペーサと他のスペーサとの冷却材の流量分布を比較したものであり、ａ図は計測する場所を示し、ｂ図は比較した線図である。The flow rate distribution of the coolant of the spacer by this invention and another spacer is compared, a figure shows the place to measure and b figure is a compared diagram. 別の発明の燃料集合体と従来の燃料集合体との圧力損失の軸方向分布を比較した線図である。It is the diagram which compared the axial direction distribution of the pressure loss of the fuel assembly of another invention, and the conventional fuel assembly. 図１０と同様の場合の液膜厚さの軸方向変化を標準ケースと比較した線図である。It is the diagram which compared the axial direction change of the liquid film thickness in the case similar to FIG. 10 with the standard case. ＢＷＲ及びＢＷＲ用燃料集合体の構成を示す説明図である。It is explanatory drawing which shows the structure of the fuel assembly for BWR and BWR. ＢＷＲにおける冷却水の二相流の様子を示す拡大断面図である。It is an expanded sectional view which shows the mode of the two-phase flow of the cooling water in BWR. 燃料棒表面の冷却水流れの様子と温度分布を示す説明図である。It is explanatory drawing which shows the mode of the cooling water flow on a fuel rod surface, and temperature distribution. 従来のミキシングベーン付きスペーサの構成を示す説明図である。It is explanatory drawing which shows the structure of the conventional spacer with a mixing vane. 従来のフロータブ付きスペーサの構成を示す説明図である。It is explanatory drawing which shows the structure of the conventional spacer with a flow tab. 従来の限界出力の向上に寄与するスペーサに備わった管状フェルールの構成を示す説明図である。It is explanatory drawing which shows the structure of the tubular ferrule with which the spacer which contributes to the improvement of the conventional limit output was equipped. 従来の限界出力の向上に寄与するスペーサに備わったねじり翼の構成を示す説明図である。It is explanatory drawing which shows the structure of the torsion blade provided in the spacer which contributes to the improvement of the conventional limit output.

Claims (3)

上部タイプレートと下部タイプレートとの間に平行配列された燃料棒を含む複数の棒状要素を、これら棒状要素を相互に間隔を開けて保持する複数のスペーサによって、バンドル状に装荷した沸騰水型原子炉用燃料集合体において、
最下位及び最上位のスペーサにミキシングベーンとフロータブとを実質的に具備せず、その他のスペーサにミキシングベーン及びフロータブを具備したことを特徴とする沸騰水型原子炉用燃料集合体。 A boiling water type in which a plurality of rod-shaped elements including fuel rods arranged in parallel between the upper tie plate and the lower tie plate are loaded in a bundle by a plurality of spacers holding the rod-shaped elements spaced apart from each other. In the nuclear fuel assembly,
A fuel assembly for a boiling water reactor, wherein the lowermost and uppermost spacers are substantially not provided with mixing vanes and flow tabs, and the other spacers are provided with mixing vanes and flow tabs. 最下位から２番目のスペーサについてもミキシングベーンとフロータブとを実質的に具備しないことを特徴とする請求項１に記載の沸騰水型原子炉用燃料集合体。   2. The fuel assembly for a boiling water reactor according to claim 1, wherein the second lowest spacer is substantially free of mixing vanes and flow tabs. 前記ミキシングベーンとフロータブとを実質的に具備しないスペーサに、１面あたり２個程度のガイドインタブを具備したことを特徴とする請求項１又は２に記載の沸騰水型原子炉用燃料集合体。
3. The fuel assembly for a boiling water reactor according to claim 1, wherein the spacer that does not substantially include the mixing vane and the flow tab includes about two guide-in tabs per surface. 4.
JP2003282419A 2003-07-30 2003-07-30 Fuel assembly for boiling water reactor Pending JP2005049256A (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007040876A (en) * 2005-08-04 2007-02-15 Nuclear Fuel Ind Ltd Fuel assembly spacer for boiling water reactor, and the fuel assembly
JP2009092416A (en) * 2007-10-04 2009-04-30 Global Nuclear Fuel-Japan Co Ltd Fuel spacer, fuel assembly, and reactor core
JP2014126516A (en) * 2012-12-27 2014-07-07 Hitachi Ltd Fuel assembly

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007040876A (en) * 2005-08-04 2007-02-15 Nuclear Fuel Ind Ltd Fuel assembly spacer for boiling water reactor, and the fuel assembly
JP4573330B2 (en) * 2005-08-04 2010-11-04 原子燃料工業株式会社 Boiling water reactor fuel assembly spacer and fuel assembly
JP2009092416A (en) * 2007-10-04 2009-04-30 Global Nuclear Fuel-Japan Co Ltd Fuel spacer, fuel assembly, and reactor core
JP2014126516A (en) * 2012-12-27 2014-07-07 Hitachi Ltd Fuel assembly
US9646724B2 (en) 2012-12-27 2017-05-09 Hitachi, Ltd. Fuel assembly

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