JPH10170674A - Fuel assembly - Google Patents
Fuel assemblyInfo
- Publication number
- JPH10170674A JPH10170674A JP8328200A JP32820096A JPH10170674A JP H10170674 A JPH10170674 A JP H10170674A JP 8328200 A JP8328200 A JP 8328200A JP 32820096 A JP32820096 A JP 32820096A JP H10170674 A JPH10170674 A JP H10170674A
- Authority
- JP
- Japan
- Prior art keywords
- fuel
- fuel assembly
- outermost periphery
- rods
- uranium
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
- Y02E30/30—Nuclear fission reactors
Landscapes
- Monitoring And Testing Of Nuclear Reactors (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は燃料集合体に関す
る。[0001] The present invention relates to a fuel assembly.
【０００２】[0002]
【従来の技術】原子炉では、一定出力を得るのに必要な
核分裂物質量を減らし、燃料経済性を高めることが望ま
れている。これに対処するため、燃料棒の上端部及び下
端部における核分裂性物質の濃縮度を中央部より低下さ
せることにより軸方向に核分裂物質濃度分布をもたせ、
上下端部からの中性子の漏れを低減させることによって
燃料経済性を向上させる方法が一般に用いられている。2. Description of the Related Art In a nuclear reactor, it is desired to reduce the amount of fissile material required to obtain a constant output and to improve fuel economy. In order to cope with this, the concentration of fissile material at the upper end and lower end of the fuel rod is made lower than that at the center, thereby giving the fissile material concentration distribution in the axial direction,
A method is generally used to improve fuel economy by reducing neutron leakage from the upper and lower ends.
【０００３】例えば、特開昭59−38684 号公報には、燃
料有効部の上端から燃料有効長の２／２４の長さを有す
る上端部及び燃料有効部の下端から燃料有効長の１／２
４の長さを有する下端部をもち、上下端部に対して天然
ウラン燃料を装荷した構成が記載されている。For example, Japanese Patent Application Laid-Open No. 59-38684 discloses an upper end portion having a length of 2/24 of the active fuel length from the upper end of the active fuel portion and a half of the active fuel length from the lower end of the active fuel portion.
It describes a configuration having a lower end portion having a length of 4 and loading natural uranium fuel on the upper and lower end portions.
【０００４】また、特開昭62−140091号公報には、部分
長水ロッドを用いた燃料集合体で、部分長水ロッドの上
方にある燃料有効部のうち、水ロッドに最近接している
燃料棒に対して天然ウラン燃料を装荷し、かつ燃料集合
体の最外周に装荷された燃料棒の平均ウラン濃縮度に対
して最外周以外に装荷された燃料棒の平均ウラン濃縮度
が小さくなるような構成が記載されている。また、同公
報には燃料集合体の最外周は燃料集合体外を流れる水に
隣接しているため、水分子との衝突によってエネルギを
失った熱中性子の多い領域であること、この熱中性子は
ウラン２３５と核反応を起こしやすく、熱中性子の多い
燃料集合体の最外周領域に高濃縮度のウラン燃料を装荷
することにより、均一にウラン燃料を装荷するのに比べ
て効率よくウラン燃料を反応させることが可能であるた
め、同公報に記載されている構造をとることにより部分
長水ロッドの上方で反応度を増加させることが可能であ
ることが記載されている。Japanese Unexamined Patent Publication No. Sho 62-140091 discloses a fuel assembly using a partial length water rod, which includes a fuel effective portion located above the partial length water rod and which is closest to the water rod. The rods are loaded with natural uranium fuel, and the average uranium enrichment of the fuel rods loaded at other than the outermost circumference is smaller than the average uranium enrichment of the fuel rods loaded at the outermost circumference of the fuel assembly. Is described. According to the same publication, since the outermost periphery of the fuel assembly is adjacent to water flowing outside the fuel assembly, it is a region having a large amount of thermal neutrons that have lost energy due to collision with water molecules, and this thermal neutron is uranium. By loading highly enriched uranium fuel in the outermost peripheral region of a fuel assembly that easily causes a nuclear reaction with H.235 and has a large amount of thermal neutrons, the uranium fuel reacts more efficiently than loading uranium fuel uniformly. It is described that the reactivity described above can be increased above the partial length water rod by adopting the structure described in the publication.
【０００５】[0005]
【発明が解決しようとする課題】特開昭59−38684 号公
報に記載されている燃料集合体構成では、上下端部から
の中性子の漏れが小さくなることによって燃料経済性は
向上するが、上下端部に装荷された天然ウランによって
上下端部出力が低下することにより、天然ウラン燃料を
上下端部に装荷しない時に比べて軸方向出力ピーキング
係数が増加する傾向がある。The fuel assembly described in Japanese Patent Application Laid-Open No. 59-38684 improves fuel economy by reducing neutron leakage from the upper and lower ends. Since the output of the upper and lower ends is reduced by the natural uranium loaded at the end, the axial output peaking coefficient tends to increase as compared with when the natural uranium fuel is not loaded at the upper and lower ends.
【０００６】軸方向出力ピーキング係数とは炉心軸方向
の熱出力を相対的に表した軸方向相対出力の最大値であ
る。軸方向相対出力とは、軸方向に対して和をとると軸
方向分割数（定数）になるように熱出力を相対化したも
のである。この軸方向出力ピーキング係数と上下端部出
力の関係を示した一例が図７である。このように熱出力
を軸方向分割数（定数）で相対化（軸方向相対出力値と
Ｘ軸で囲まれた部分の面積が一定）してあることによ
り、上下端部の相対出力が増大すれば中央部の相対出力
が減少し、軸方向出力ピーキング係数も減少する。言い
換えれば燃料集合体における軸方向出力ピーキング係数
の値が小さいことが燃料集合体の熱的余裕が大きいこと
に対応している。[0006] The axial power peaking coefficient is the maximum value of the axial relative power which relatively represents the thermal power in the axial direction of the core. The axial relative output is a relative value of the thermal output such that the sum in the axial direction is equal to the axial division number (constant). FIG. 7 shows an example showing the relationship between the axial output peaking coefficient and the upper and lower end outputs. Since the thermal output is made relative by the number of axial divisions (constant) (the relative output value in the axial direction and the area of the portion enclosed by the X axis are constant), the relative output of the upper and lower ends increases. For example, the relative output at the center decreases, and the axial output peaking coefficient also decreases. In other words, a small value of the axial output peaking coefficient in the fuel assembly corresponds to a large thermal margin of the fuel assembly.
【０００７】また、特開昭62−140091号公報に記載され
ている燃料集合体構成では軸方向ガドリニア分布につい
て完全に考慮されておらず、また部分長水ロッドの長さ
を用いて上部領域が定められているため、軸方向出力分
布の平坦化には有効ではなかった。Further, in the fuel assembly configuration disclosed in Japanese Patent Application Laid-Open No. Sho 62-140091, the gadolinia distribution in the axial direction is not completely considered, and the upper region is formed by using the length of the partial length water rod. Because it is determined, it is not effective for flattening the axial power distribution.
【０００８】本発明の目的は、従来の燃料集合体のもつ
燃料経済性をほぼ維持しつつ、軸方向出力ピーキング係
数を低減可能な燃料集合体を提供することにある。An object of the present invention is to provide a fuel assembly capable of reducing the axial output peaking coefficient while substantially maintaining the fuel economy of the conventional fuel assembly.
【０００９】[0009]
【課題を解決するための手段】上記目的を達成するた
め、本発明の燃料集合体は、格子状に配置された複数の
燃料棒からなる燃料集合体で、前記燃料棒の燃料有効部
は上端部，中央部，下端部の三領域からなり、前記上端
部は前記燃料有効部の全長の１／２４〜２／２４の長さ
を、前記下端部は前記燃料有効部の全長の１／２４の長
さを有し、前記燃料集合体最外周の前記燃料棒の平均核
分裂物質濃度が最外周以外の前記燃料棒の平均核分裂物
質濃度よりも小さい水平断面構造を前記中央部の全領域
に有し、かつ前記燃料集合体最外周の前記燃料棒の平均
核分裂物質濃度が最外周以外の前記燃料棒の平均核分裂
物質濃度よりも大きく、かつ可燃性毒物を含まない水平
断面構造を前記上端部及び前記下端部の全領域もしくは
その一部に有することにその特徴を有している。In order to achieve the above object, a fuel assembly according to the present invention is a fuel assembly comprising a plurality of fuel rods arranged in a grid, and a fuel effective portion of the fuel rod has an upper end. Part, a central part, and a lower end part. The upper end part is 1/24 to 2/24 of the total length of the active fuel part, and the lower end part is 1/24 of the total length of the active fuel part. And a horizontal cross-sectional structure having an average fissile material concentration of the fuel rods at the outermost periphery of the fuel assembly that is smaller than an average fissile material concentration of the fuel rods other than the outermost periphery. And, the average fission material concentration of the fuel rods at the outermost periphery of the fuel assembly is larger than the average fissile material concentration of the fuel rods other than the outermost periphery, and the horizontal cross-sectional structure containing no burnable poison is the upper end portion and The entire lower end area or part of the lower end area It has its features.
【００１０】燃料集合体間を流れる水に隣接している燃
料集合体の最外周の燃料棒は、水に隣接していない他の
燃料棒に比べて原子炉全体の出力に対する寄与が大き
い。そのため本発明のように、燃料集合体の最外周の燃
料棒の平均核分裂物質濃度が最外周以外の燃料棒の平均
核分裂物質濃度よりも大きく、かつ可燃性毒物を含まな
い上下端部水平断面構造を採用することにより、同じウ
ラン量でも上下端部の反応度を高めることができる。こ
れによって炉心の反応度も高まり、また上下端部の相対
出力も高まるので軸方向出力ピーキング係数を低減する
ことができる。しかし、燃料集合体の最外周に高濃縮度
燃料を装荷する本発明の構造を採用すると、燃料集合体
最外周で局所的に熱出力が増加することになる。以下に
示す図１〜図５の燃料集合体の計算結果から、軸方向出
力ピーキング係数の平均的な値は約１.２ であることが
分かっている。この結果より、軸方向相対出力が軸方向
出力ピーキング係数の半分の値である０.６ 以下の領域
に対して本発明を採用すれば、本発明の上端部及び下端
部が熱的な制限を越えることはないと考えられる。図６
より、上記の条件を満たす領域は燃料有効部下端から燃
料有効部の全長の１／２４以内、燃料有効部上端から燃
料有効部の全長の２／２４以内であることがわかる。つ
まり前記の領域では燃料集合体の上下端部水平断面の最
外周の燃料棒の相対出力は高くなるものの、そもそも低
出力密度の部分に本発明の実施範囲を限定してあるので
熱的な制限値を超えることはない。[0010] The outermost fuel rods of the fuel assembly adjacent to the water flowing between the fuel assemblies make a greater contribution to the power of the entire reactor than other fuel rods not adjacent to the water. Therefore, as in the present invention, the average fission material concentration of the fuel rods at the outermost periphery of the fuel assembly is higher than the average fission material concentration of the fuel rods other than the outermost periphery, and the upper and lower end horizontal cross-sectional structures containing no burnable poisons By adopting, the reactivity of the upper and lower ends can be increased even with the same uranium amount. As a result, the reactivity of the core is increased, and the relative output of the upper and lower ends is also increased, so that the axial power peaking coefficient can be reduced. However, when the structure of the present invention in which the outermost periphery of the fuel assembly is loaded with the highly enriched fuel is adopted, the heat output locally increases at the outermost periphery of the fuel assembly. From the calculation results of the fuel assemblies shown in FIGS. 1 to 5 shown below, it is known that the average value of the axial output peaking coefficient is about 1.2. According to this result, if the present invention is applied to a region where the relative output in the axial direction is 0.6 or less, which is half the value of the peaking coefficient in the axial direction, the upper end and the lower end of the present invention have no thermal limitation. It is not expected to exceed. FIG.
From the above, it can be seen that the region satisfying the above condition is within 1/24 of the total length of the active fuel portion from the lower end of the active fuel portion, and within 2/24 of the total length of the active fuel portion from the upper end of the active fuel portion. In other words, although the relative output of the outermost fuel rods in the horizontal cross section of the upper and lower ends of the fuel assembly becomes higher in the above-mentioned region, the scope of the present invention is limited to a portion having a low power density in the first place. Never exceed the value.
【００１１】[0011]
【発明の実施の形態】以下、本発明を図１ないし図５を
用いて説明する。図１は本発明の燃料集合体の一実施例
として、特開昭62−140091公報に記載されている構成に
対して本発明を適用した燃料集合体の水平断面図及び各
燃料棒のウラン濃縮度とガドリニアの分布図である。図
中、１〜７の整数は燃料棒の種類を表しており、上方の
燃料集合体水平断面の番号と、下方の燃料棒の番号とが
対応している。８は部分長水ロッドである。また燃料棒
中に記載されている数字はウラン濃縮度、その後に付記
されている数字はガドリニア濃縮度であり、燃料棒上下
端部の斜線部分は天然ウランである。また燃料棒の軸方
向濃縮度分布図の左側に付記されている分数は燃料有効
部の全長を１としたときの各々の領域の長さを表してい
る。図１は特開昭62−140091号公報に記載されている燃
料集合体構造と異なり、天然ウラン燃料を上端から１／
２４〜２／２４の間の上端部にのみ装荷しており、上端
部に対して可燃性毒物であるガドリニアを使用していな
いことが特徴である。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to FIGS. FIG. 1 shows a horizontal sectional view of a fuel assembly to which the present invention is applied with respect to the structure described in Japanese Patent Application Laid-Open No. 62-14091, and uranium enrichment of each fuel rod as one embodiment of the fuel assembly of the present invention. It is a distribution map of a degree and gadolinia. In the drawing, the integers 1 to 7 represent the types of the fuel rods, and the numbers of the upper fuel assembly horizontal cross section correspond to the numbers of the lower fuel rods. 8 is a partial length water rod. The numbers described in the fuel rods are the uranium enrichment, the numbers attached after them are the gadolinia enrichment, and the hatched portions at the upper and lower ends of the fuel rods are natural uranium. The fractions added on the left side of the fuel rod axial enrichment distribution diagram represent the length of each region when the total length of the active fuel portion is set to 1. FIG. 1 is different from the fuel assembly structure described in JP-A-62-140091 in that natural uranium fuel is 1 /
Only the upper end between 24 and 2/24 is loaded, and gadolinia which is a burnable poison is not used for the upper end.
【００１２】まず、本発明の燃料集合体構成と特開昭62
−140091号公報に記載されている燃料集合体構成とを比
較することにより、その相違点について簡単に説明す
る。二つの燃料集合体構成について各々計算すると、軸
方向出力ピーキング係数は特開昭62−140091号公報記載
の構造に比べて約５％の低減、燃料経済性は約２％の改
善となった。但し、燃料経済性を次式で定義し、異なる
平均ウラン濃縮度を有する燃料集合体間で燃料経済性を
比較するための相対的な指標として採用している。燃料
経済性≡Ｅ／(ｅp−ｅd)、但し、ｅp ：燃料集合体の平
均ウラン濃縮度、ｅd ：廃棄材ウラン濃縮度（〜０.２
ｗｔ.％）、Ｅ：取り出し燃焼度。First, the structure of the fuel assembly of the present invention and Japanese Patent Application Laid-Open
The differences will be briefly described by comparing with the fuel assembly configuration described in JP-A-140091. Calculations for each of the two fuel assembly configurations showed that the axial output peaking factor was reduced by about 5% and the fuel economy was improved by about 2% compared to the structure described in JP-A-62-140091. However, the fuel economy is defined by the following equation, and is used as a relative index for comparing the fuel economy between fuel assemblies having different average uranium enrichment. Fuel economy ≡E / (e p -e d) , where, e p: mean uranium enrichment of the fuel assembly, e d: waste material uranium enrichment (0.2
wt.%), E: take-out burnup.
【００１３】次に軸方向相対出力分布を図７に示す。図
７から本発明の作用である、上端部の出力増大により相
対的に中央部出力が低下し、結果として軸方向相対出力
の最大値である軸方向出力ピーキング係数が低減してい
ることがわかる。このように本発明の構造は燃料経済性
向上と軸方向出力ピーキング係数を低減することが可能
であり、その作用効果，構成で特開昭62−140091号公報
とは明らかに異なっている。FIG. 7 shows the relative output distribution in the axial direction. From FIG. 7, it can be seen that the output of the central portion is relatively reduced due to the increase in the output of the upper end portion, which is the effect of the present invention, and as a result, the axial output peaking coefficient which is the maximum value of the axial relative output is reduced. . As described above, the structure of the present invention is capable of improving fuel economy and reducing the axial output peaking coefficient, and is clearly different from JP-A-62-140091 in its operation, effect, and configuration.
【００１４】以下、従来の燃料集合体として図２を設定
し、本発明の燃料集合体構成のもつ効果を示す。図中の
記号，数字などに関しては先に説明した通りである。燃
料集合体内の全燃料棒に対して燃料有効部の上端部及び
下端部が各々同じ長さでかつ一様な天然ウランを装荷し
ていることが従来の燃料集合体である図２の特徴であ
る。これに対して図１は本発明である、燃料集合体最外
周の燃料棒の平均核分裂物質濃度が最外周以外の燃料棒
の平均核分裂物質濃度よりも大きく、かつ可燃性毒物を
含まない水平断面構造を燃料有効部上端から燃料有効部
の全長の１／２４〜２／２４の部位に有していることが
特徴である。この上端部構造の相違の結果、上端から燃
料有効部の全長の１／２４〜２／２４の部位の水平断面
の平均ウラン濃縮度が高いことによる若干の燃料経済性
の低下，高濃縮ウラン燃料を燃料集合体の最外周に配置
することによる反応度の増大とそれに伴う取り出し燃焼
度の増大と燃料経済性の向上，上端部が高出力になるこ
とによる軸方向出力ピーキング係数の低減、と三つの作
用が起こり、従来構造のもつ燃料経済性をほぼ維持しつ
つ、軸方向出力ピーキング係数を約２％低減することが
可能である。Hereinafter, FIG. 2 is set as a conventional fuel assembly, and the effect of the fuel assembly configuration of the present invention is shown. The symbols and numerals in the figure are as described above. A feature of the conventional fuel assembly shown in FIG. 2 is that the natural upper uranium and the lower end of the active fuel portion are all loaded with the same length and uniform natural uranium for all the fuel rods in the fuel assembly. is there. On the other hand, FIG. 1 shows a horizontal cross section of the present invention, in which the average fissile material concentration of the fuel rods at the outermost periphery of the fuel assembly is higher than the average fissionable material concentration of the fuel rods other than the outermost periphery and does not contain burnable poisons. It is characterized in that the structure is provided at a position 1/24 to 2/24 of the total length of the fuel effective portion from the upper end of the fuel effective portion. As a result of this difference in the upper end structure, a slight decrease in fuel economy due to a high average uranium enrichment in a horizontal section of 1/24 to 2/24 of the total length of the fuel effective portion from the upper end, and a high enriched uranium fuel By increasing the reactivity of the fuel assembly at the outermost periphery of the fuel assembly, thereby increasing the take-out burnup and improving fuel economy, and reducing the axial output peaking coefficient by increasing the output power at the upper end. One effect is that it is possible to reduce the axial output peaking factor by about 2% while substantially maintaining the fuel economy of the conventional structure.
【００１５】また、図３は本発明の他の実施例であり、
図１と同様に燃料集合体の水平断面図及び各燃料棒のウ
ラン濃縮度とガドリニアの分布図を表したものである。
これは先の実施例である図１と比べて、上端部に使用し
ている天然ウラン量が少なく、そのため上端部全体が、
燃料集合体最外周の燃料棒の平均核分裂物質濃度が最外
周以外の燃料棒の平均核分裂物質濃度よりも大きく、か
つ可燃性毒物を含まない水平断面構造となっている。こ
の実施例と図１とを比較した場合、上端部の平均ウラン
濃縮度が更に高いことによる燃料経済性の若干の低下、
上端部が更に高出力になることによる軸方向出力ピーキ
ング係数の低減が起こり、図１の実施例に比べて燃料経
済性は約１％低下、軸方向出力ピーキング係数は約１％
の低減となる。従来例と比較すると、燃料経済性は約１
％低下するが、軸方向出力ピーキング係数が約３％の低
減となり、軸方向出力ピーキング係数の改善効果を増大
できる。FIG. 3 shows another embodiment of the present invention.
FIG. 2 shows a horizontal sectional view of a fuel assembly and a distribution diagram of uranium enrichment and gadolinia of each fuel rod as in FIG. 1.
This is because the amount of natural uranium used at the upper end is smaller than that of FIG.
The fuel rods at the outermost periphery of the fuel assembly have an average fission material concentration higher than the average fissionable material concentrations of the fuel rods other than the outermost periphery, and have a horizontal cross-sectional structure that does not contain burnable poisons. Comparing this example with FIG. 1, a slight decrease in fuel economy due to the higher average uranium enrichment at the upper end,
A higher output at the upper end results in a reduction in the axial power peaking factor, which reduces fuel economy by about 1% and an axial power peaking factor by about 1% compared to the embodiment of FIG.
Is reduced. Compared with the conventional example, the fuel economy is about 1
%, The axial output peaking coefficient is reduced by about 3%, and the effect of improving the axial output peaking coefficient can be increased.
【００１６】また、図４は本発明の他の実施例であり、
図１と同様に燃料集合体の水平断面図及び各燃料棒のウ
ラン濃縮度とガドリニアの分布図を表したものである。
これは先の実施例である図３と比べて上端部が燃料有効
部の全長の１／２４しかない構造となっている。この実
施例と図３とを比較した場合、中央部が長くなることに
よって上端部付近の熱出力が高くなることによる軸方向
出力ピーキング係数の低減が起こり、図３の実施例に比
べて燃料経済性をほぼ維持しつつ、軸方向出力ピーキン
グ係数を更に約１％低減することができる。従来例と比
較すると、軸方向出力ピーキング係数が約４％の低減と
なり、図４の燃料集合体構成を用いることによっても、
燃料経済性をほぼ維持しつつ、軸方向出力ピーキング係
数を大幅に低減できる。FIG. 4 shows another embodiment of the present invention.
FIG. 2 shows a horizontal sectional view of a fuel assembly and a distribution diagram of uranium enrichment and gadolinia of each fuel rod as in FIG. 1.
This has a structure in which the upper end portion is only 1/24 of the total length of the fuel effective portion as compared with FIG. 3 which is the previous embodiment. When this embodiment is compared with FIG. 3, the axial output peaking coefficient is reduced due to the increase of the heat output near the upper end portion due to the longer central portion, and the fuel economy is lower than that of the embodiment of FIG. The axial output peaking factor can be further reduced by about 1% while maintaining the performance. Compared with the conventional example, the axial output peaking coefficient is reduced by about 4%, and by using the fuel assembly configuration of FIG.
The axial output peaking factor can be significantly reduced while maintaining fuel economy.
【００１７】また、図５は本発明の他の実施例であり、
図１と同様に燃料集合体の水平断面図及び各燃料棒のウ
ラン濃縮度とガドリニアの分布図を表したものである。
この実施例は図２（従来例）の下端から燃料有効部の全
長の１／２４の範囲に装荷されている天然ウランに対し
て本発明の構造を適用したものである。この実施例と従
来例とを比較した場合、下端部の平均ウラン濃縮度が高
いことによる燃料経済性の若干の低下，高濃縮ウラン燃
料を燃料集合体の最外周に配置することによる反応度の
増大とそれに伴う燃料経済性の向上，下端部が高出力に
なることによる軸方向出力ピーキング係数の低減と三つ
の作用が起こり、従来構造のもつ燃料経済性をほぼ維持
しつつ、軸方向出力ピーキング係数を約２％低減するこ
とが可能である。FIG. 5 shows another embodiment of the present invention.
FIG. 2 shows a horizontal sectional view of a fuel assembly and a distribution diagram of uranium enrichment and gadolinia of each fuel rod as in FIG. 1.
In this embodiment, the structure of the present invention is applied to natural uranium loaded in the range of 1/24 of the total length of the active fuel portion from the lower end of FIG. 2 (conventional example). When this embodiment is compared with the conventional example, the fuel economy is slightly reduced due to the high average uranium enrichment at the lower end, and the reactivity is reduced by arranging the highly enriched uranium fuel at the outermost periphery of the fuel assembly. Increase in fuel economy and the resulting increase in fuel economy, reduction in axial output peaking coefficient due to higher output at the lower end, and three effects occur. Axial output peaking while substantially maintaining the fuel economy of the conventional structure The factor can be reduced by about 2%.
【００１８】なお、上記四つの実施例では上端部のみ、
もしくは下端部のみに本発明の構造を採用しているが上
端部，下端部双方を同時に本発明の構造にすることも可
能である。In the above four embodiments, only the upper end portion is provided.
Alternatively, the structure of the present invention is adopted only at the lower end, but both the upper end and the lower end may have the structure of the present invention at the same time.
【００１９】また、上記四つの実施例ではウラン燃料を
使用した燃料集合体を採用したが、ウラン燃料だけでな
くＭＯＸ燃料を装荷した燃料集合体を使用することも可
能である。In the above four embodiments, a fuel assembly using uranium fuel is employed. However, a fuel assembly loaded with MOX fuel as well as uranium fuel can be used.
【００２０】また、上記四つの実施例では燃料集合体を
構成する燃料棒として長尺燃料棒のみを使用している
が、複数本の短尺燃料棒を併用する燃料集合体構成に対
しても本発明を適用することが可能である。なぜなら本
発明は燃料集合体の上下端部の構造に関するものであ
り、燃料集合体の中央部の具体的な構造にはほぼ依存し
ないからである。In the above four embodiments, only long fuel rods are used as fuel rods constituting a fuel assembly. However, the present invention is also applicable to a fuel assembly configuration in which a plurality of short fuel rods are used in combination. The invention can be applied. This is because the present invention relates to the structure of the upper and lower ends of the fuel assembly and does not substantially depend on the specific structure of the center of the fuel assembly.
【００２１】また、上記四つの実施例では燃料集合体中
央部に燃料棒より太径の２本の水ロッドを配置した燃料
集合体について説明したが、燃料集合体中央部に方形断
面を有する１本の水ロッドを配置した図６のような燃料
集合体構成を用いることも可能である。In the above four embodiments, the fuel assembly in which two water rods having a diameter larger than that of the fuel rod are arranged at the center of the fuel assembly has been described. It is also possible to use a fuel assembly configuration as shown in FIG. 6 in which the water rods are arranged.
【００２２】また、上記四つの実施例では上下端部に天
然ウラン燃料を用いているが、天然ウランの代わりに劣
化ウランを用いることも可能である。なぜならば上記で
説明した作用効果，燃料集合体最外周に高濃縮度のウラ
ン燃料を装荷して反応度を増大し、燃料経済性を向上さ
せること及び端部出力を増大させて軸方向出力ピーキン
グ係数を低減することは、劣化ウラン，天然ウランのど
ちらを上下端部に装荷するかには依存しないからであ
る。In the above four embodiments, natural uranium fuel is used for the upper and lower ends, but depleted uranium can be used instead of natural uranium. This is because the above-described operation and effect are achieved by loading a highly enriched uranium fuel on the outermost periphery of the fuel assembly to increase the reactivity, thereby improving the fuel economy, and increasing the end output to increase the axial output peaking. This is because reducing the coefficient does not depend on whether depleted uranium or natural uranium is loaded on the upper and lower ends.
【００２３】[0023]
【発明の効果】本発明によれば燃料経済性をほぼ維持し
つつ、軸方向出力ピーキング係数を低減することが可能
である。According to the present invention, it is possible to reduce the axial output peaking coefficient while substantially maintaining fuel economy.
【図１】本発明の燃料集合体の一実施例を示す各燃料棒
のウラン濃縮度とガドリニアの分布図。FIG. 1 is a distribution diagram of uranium enrichment and gadolinia of each fuel rod showing one embodiment of the fuel assembly of the present invention.
【図２】従来の燃料集合体の各燃料棒のウラン濃縮度と
ガドリニアの分布図。FIG. 2 is a distribution diagram of uranium enrichment and gadolinia of each fuel rod of a conventional fuel assembly.
【図３】本発明の他の実施例を示す各燃料棒のウラン濃
縮度とガドリニアの分布図。FIG. 3 is a distribution diagram of uranium enrichment and gadolinia of each fuel rod showing another embodiment of the present invention.
【図４】本発明の他の実施例を示す各燃料棒のウラン濃
縮度とガドリニアの分布図。FIG. 4 is a distribution diagram of uranium enrichment and gadolinia of each fuel rod showing another embodiment of the present invention.
【図５】本発明の他の実施例を示す各燃料棒のウラン濃
縮度とガドリニアの分布図。FIG. 5 is a distribution diagram of uranium enrichment and gadolinia of each fuel rod showing another embodiment of the present invention.
【図６】本発明を適用可能な方形断面水ロッドを有する
燃料集合体の説明図。FIG. 6 is an explanatory view of a fuel assembly having a rectangular cross-section water rod to which the present invention can be applied.
【図７】図１と特開昭62−140091号公報に記載されてい
る燃料集合体構成との軸方向相対出力の相違を示す特性
図。FIG. 7 is a characteristic diagram showing a difference in an axial relative output between FIG. 1 and a fuel assembly configuration described in JP-A-62-140091.
１〜７…燃料棒の種類、８…部分長水ロッド。 1-7: Types of fuel rods, 8: Partially long water rods.
Claims (4)
燃料集合体において、前記燃料棒の燃料有効部は上端
部，中央部，下端部の三領域からなり、前記上端部は前
記燃料有効部の全長の１／２４〜２／２４の長さを、前
記下端部は前記燃料有効部の全長の１／２４の長さを有
し、前記燃料集合体最外周の前記燃料棒の平均核分裂物
質濃度が最外周以外の前記燃料棒の平均核分裂物質濃度
よりも小さい水平断面構造を前記中央部の全領域に有
し、前記燃料集合体最外周の前記燃料棒の平均核分裂物
質濃度が最外周以外の前記燃料棒の平均核分裂物質濃度
よりも大きく、可燃性毒物を含まない水平断面構造を前
記上端部及び前記下端部の全領域もしくはその一部に有
することを特徴とする燃料集合体。1. A fuel assembly comprising a plurality of fuel rods arranged in a lattice, wherein a fuel effective portion of the fuel rod comprises three regions of an upper end, a center, and a lower end, and the upper end is provided with the fuel rod. The lower end has a length of 1/24 of the total length of the active fuel portion, and the lower end has a length of 1/24 of the total length of the active fuel portion. The central region has a horizontal cross-sectional structure in which the fissile material concentration is smaller than the average fissile material concentration of the fuel rods other than the outermost periphery, and the average fissile material concentration of the fuel rods at the outermost periphery of the fuel assembly is the highest. A fuel assembly having a horizontal cross-sectional structure that is higher than the average fissile material concentration of the fuel rods other than the outer periphery and does not contain burnable poisons, in the entire upper end portion and the lower end portion or a part thereof.
請求項１に記載の燃料集合体。2. The fuel assembly according to claim 1, wherein uranium fuel is used as the fission material.
効部の上下端に近接する前記上下端部の一部もしくはそ
の全領域に天然ウラン、もしくは劣化ウラン燃料を装荷
し、天然ウラン、もしくは劣化ウラン領域の上下端から
の長さが異なる複数の燃料棒の燃料集合体内における配
置によって、燃料集合体最外周の燃料棒の平均核分裂物
質濃度が最外周以外の燃料棒の平均核分裂物質濃度より
も大きく、かつ可燃性毒物を含まない水平断面構造を上
下端部に実現する請求項１に記載の燃料集合体。3. A natural uranium or depleted uranium fuel is loaded on the upper and lower ends of the fuel effective portion at a part or the entire area of the upper and lower ends close to the upper and lower ends of the fuel effective portion. Alternatively, depending on the arrangement in the fuel assembly of a plurality of fuel rods having different lengths from the upper and lower ends of the depleted uranium region, the average fissile material concentration of the fuel rods at the outermost periphery of the fuel assembly may be increased. The fuel assembly according to claim 1, wherein a horizontal cross-sectional structure having a concentration higher than the concentration and containing no burnable poison is realized at the upper and lower ends.
端部に天然ウラン、もしくは劣化ウランを用い、前記燃
料集合体最外周は上端部及び下端部に隣接する中央部燃
料のウラン濃縮度を上端部及び下端部として用いること
によって、前記燃料集合体最外周の燃料棒の平均核分裂
物質濃度が最外周以外の燃料棒の平均核分裂物質濃度よ
りも大きく、可燃性毒物を含まない水平断面構造を上下
端部に実現する請求項１に記載の燃料集合体。4. Uranium enrichment of central fuel adjacent to upper and lower ends of the fuel assembly, wherein natural uranium or depleted uranium is used at the upper and lower ends of the fuel rods other than the outermost periphery of the fuel assembly. The average fission material concentration of the fuel rods at the outermost periphery of the fuel assembly is larger than the average fission material concentration of the fuel rods other than the outermost periphery by using the degrees as the upper end portion and the lower end portion. The fuel assembly according to claim 1, wherein the structure is realized at upper and lower ends.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP32820096A JP3525657B2 (en) | 1996-12-09 | 1996-12-09 | Fuel assembly |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP32820096A JP3525657B2 (en) | 1996-12-09 | 1996-12-09 | Fuel assembly |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH10170674A true JPH10170674A (en) | 1998-06-26 |
| JP3525657B2 JP3525657B2 (en) | 2004-05-10 |
Family
ID=18207575
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP32820096A Expired - Fee Related JP3525657B2 (en) | 1996-12-09 | 1996-12-09 | Fuel assembly |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3525657B2 (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6343106B1 (en) | 1998-08-27 | 2002-01-29 | Kabushiki Kaisha Toshiba | Boiling water reactor and operation thereof |
| JP2005180929A (en) * | 2003-12-16 | 2005-07-07 | Global Nuclear Fuel-Japan Co Ltd | Fuel assembly |
| JP2011133307A (en) * | 2009-12-24 | 2011-07-07 | Global Nuclear Fuel-Japan Co Ltd | Fuel assembly for boiling water reactor and reactor core for boiling water reactor |
| JP2011221016A (en) * | 2010-04-08 | 2011-11-04 | Global Nuclear Fuel Americas Llc | Exposure boost zone for boiling water reactor nuclear bundles |
| US8311180B2 (en) | 2007-12-13 | 2012-11-13 | Hitachi, Ltd. | Fuel assembly |
-
1996
- 1996-12-09 JP JP32820096A patent/JP3525657B2/en not_active Expired - Fee Related
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6343106B1 (en) | 1998-08-27 | 2002-01-29 | Kabushiki Kaisha Toshiba | Boiling water reactor and operation thereof |
| JP2005180929A (en) * | 2003-12-16 | 2005-07-07 | Global Nuclear Fuel-Japan Co Ltd | Fuel assembly |
| US8311180B2 (en) | 2007-12-13 | 2012-11-13 | Hitachi, Ltd. | Fuel assembly |
| JP2011133307A (en) * | 2009-12-24 | 2011-07-07 | Global Nuclear Fuel-Japan Co Ltd | Fuel assembly for boiling water reactor and reactor core for boiling water reactor |
| JP2011221016A (en) * | 2010-04-08 | 2011-11-04 | Global Nuclear Fuel Americas Llc | Exposure boost zone for boiling water reactor nuclear bundles |
| US8953736B2 (en) | 2010-04-08 | 2015-02-10 | Global Nuclear Fuel—Americas, LLC | Exposure boost zone for boiling water reactor nuclear bundles |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3525657B2 (en) | 2004-05-10 |
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