JPH03267793A - Fuel assembly - Google Patents
Fuel assemblyInfo
- Publication number
- JPH03267793A JPH03267793A JP2067875A JP6787590A JPH03267793A JP H03267793 A JPH03267793 A JP H03267793A JP 2067875 A JP2067875 A JP 2067875A JP 6787590 A JP6787590 A JP 6787590A JP H03267793 A JPH03267793 A JP H03267793A
- Authority
- JP
- Japan
- Prior art keywords
- fuel
- region
- cycle
- fuel assembly
- reactor core
- 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
- 239000000446 fuel Substances 0.000 title claims abstract description 147
- 239000002574 poison Substances 0.000 claims abstract description 23
- 231100000614 poison Toxicity 0.000 claims abstract description 23
- 239000000463 material Substances 0.000 claims description 15
- 238000009826 distribution Methods 0.000 abstract description 19
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 abstract description 17
- 230000000694 effects Effects 0.000 abstract description 10
- 239000011800 void material Substances 0.000 abstract description 7
- 238000002485 combustion reaction Methods 0.000 abstract description 6
- 238000009835 boiling Methods 0.000 abstract description 4
- 238000006243 chemical reaction Methods 0.000 abstract 2
- 230000003247 decreasing effect Effects 0.000 abstract 1
- 230000036632 reaction speed Effects 0.000 abstract 1
- CMIHHWBVHJVIGI-UHFFFAOYSA-N gadolinium(iii) oxide Chemical compound [O-2].[O-2].[O-2].[Gd+3].[Gd+3] CMIHHWBVHJVIGI-UHFFFAOYSA-N 0.000 description 38
- 229910052770 Uranium Inorganic materials 0.000 description 19
- JFALSRSLKYAFGM-UHFFFAOYSA-N uranium(0) Chemical compound [U] JFALSRSLKYAFGM-UHFFFAOYSA-N 0.000 description 19
- 230000009257 reactivity Effects 0.000 description 13
- 239000008188 pellet Substances 0.000 description 7
- 238000005253 cladding Methods 0.000 description 5
- 238000001228 spectrum Methods 0.000 description 3
- FCTBKIHDJGHPPO-UHFFFAOYSA-N uranium dioxide Inorganic materials O=[U]=O FCTBKIHDJGHPPO-UHFFFAOYSA-N 0.000 description 3
- 230000000712 assembly Effects 0.000 description 2
- 238000000429 assembly Methods 0.000 description 2
- 230000004323 axial length Effects 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 125000006850 spacer group Chemical group 0.000 description 2
- JFALSRSLKYAFGM-OIOBTWANSA-N uranium-235 Chemical compound [235U] JFALSRSLKYAFGM-OIOBTWANSA-N 0.000 description 2
- 229910052778 Plutonium Inorganic materials 0.000 description 1
- 239000002826 coolant Substances 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- OOAWCECZEHPMBX-UHFFFAOYSA-N oxygen(2-);uranium(4+) Chemical compound [O-2].[O-2].[U+4] OOAWCECZEHPMBX-UHFFFAOYSA-N 0.000 description 1
- OYEHPCDNVJXUIW-UHFFFAOYSA-N plutonium atom Chemical compound [Pu] OYEHPCDNVJXUIW-UHFFFAOYSA-N 0.000 description 1
- 239000002915 spent fuel radioactive waste Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
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
【発明の詳細な説明】
［発明の目的］
（産業上の利用分野）
本発明は、沸騰水型原子炉において使用される燃料集合
体に関する。DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a fuel assembly used in a boiling water nuclear reactor.
（従来の技術）
沸騰水型（ＢＷＲ）の原子力発電所においては、多数本
の燃料棒を７×７または８×８の正方格子状に配列して
チャンネルボックス内に収納した燃料集合体を、制御棒
と共に炉内に装荷して炉心部を構成している。(Prior Art) In a boiling water type (BWR) nuclear power plant, a fuel assembly in which a large number of fuel rods are arranged in a 7x7 or 8x8 square lattice and housed in a channel box is used. It is loaded into the reactor together with the control rods to form the reactor core.
上記燃料棒としては、２〜３％の低濃縮二酸化ウランを
焼結した燃料ベレットを被覆管内に多数個充填したもの
が、従来から多用されている。また、ＢＷＲ燃料集合体
では、一般に、炉心反応度を調整するために一部の燃料
棒に可燃性毒物を混入させている。Conventionally, fuel rods in which a large number of fuel pellets made of sintered low-enriched uranium dioxide of 2 to 3% are filled in a cladding tube have been widely used. Furthermore, in a BWR fuel assembly, burnable poison is generally mixed into some of the fuel rods in order to adjust the core reactivity.
このような原子力発電所において、その経済性の向上を
図るためには、運転期間の長期化による設備利用率の向
上に対応しつつ、燃料の高燃焼度化による燃料サイクル
費を低減させることが効果的である。In order to improve the economic efficiency of such nuclear power plants, it is necessary to reduce fuel cycle costs by increasing fuel burn-up while increasing capacity utilization by extending operating periods. Effective.
燃料の高燃焼度化を図るためには、従来形の燃料を使用
し、その濃縮度を上げる方法が考えられる。In order to increase the burnup of fuel, a method can be considered that uses conventional fuel and increases its enrichment.
（発明が解決しようとする課題）
しかしながら、従来形の燃料を使用し、単にその濃縮度
を上げただけでは、中性子スペクトルの硬化が生じ、炉
心特性上、次のような現象が生じる。(Problems to be Solved by the Invention) However, if conventional fuel is used and its enrichment level is simply increased, the neutron spectrum will harden, causing the following phenomenon in terms of core characteristics.
■ボイド係数絶対値の増加
■冷温時の炉心反応度の増加
■ガドリニア等の可燃性毒物の反応度制御能力の低下
これにより、熱的余裕、炉停止余裕が減少する恐れがあ
る。■Increase in the absolute value of the void coefficient ■Increase in core reactivity at cold temperatures ■Decrease in the ability to control the reactivity of burnable poisons such as gadolinia This may reduce thermal margin and reactor shutdown margin.
また、単に濃縮度を上げるだけで高燃焼度化を図る場合
には、燃料当りに必要な天然ウラン費、濃縮費等が増加
するため、高燃焼度化による燃料サイクル費の低減幅は
小さくなる。In addition, if you aim to increase the burnup simply by increasing the enrichment, the cost of natural uranium and enrichment costs required per fuel will increase, so the reduction in fuel cycle costs due to increasing the burnup will be small. .
本発明は上記の炉心性能上の問題を解決し、可能な限り
低い濃縮度で目標とする高燃焼度化を達成することがで
きる高経済型高燃焼度燃料を提供することを目的とする
。An object of the present invention is to provide a highly economical high burnup fuel that can solve the above-mentioned core performance problems and achieve a targeted high burnup with the lowest possible enrichment.
［発明の構成］
（課題を解決するための手段）
本発明の燃料集合体は、内部に燃料物質が充填された複
数の燃料棒を有する燃料集合体において、この燃料集合
体の軸方向の領域に関し、上部領域と比べ下部領域の可
燃性毒物の平均含有量を多くし、かつその内１〜２本の
燃料棒の下部領域における単位長さ、燃料棒当りの可燃
性毒物の含有量を上部領域よりも少なくしたことを特徴
とする。[Structure of the Invention] (Means for Solving the Problems) A fuel assembly of the present invention has a fuel assembly having a plurality of fuel rods filled with a fuel substance therein. Regarding the average content of burnable poisons in the lower region compared to the upper region, the average content of burnable poisons per unit length and fuel rod in the lower region of one or two fuel rods is increased compared to the upper region. It is characterized by being smaller than the area.
（作用） 以下、本発明の作用を具体的に述べる。(effect) Hereinafter, the effects of the present invention will be specifically described.
本発明の燃料集合体では、可燃性毒物を混入させた燃料
棒の可燃性毒物の分布を集合体軸方向について２〜５領
域としている。２領域の場合（上部領域、下部領域とい
う。）には、可燃性毒物の濃度を全体的に下部領域の方
を多くする。In the fuel assembly of the present invention, the burnable poison in the fuel rods mixed with the burnable poison is distributed in 2 to 5 regions in the axial direction of the assembly. In the case of two regions (referred to as an upper region and a lower region), the overall concentration of burnable poison is increased in the lower region.
ＢＷＲでは一般にボイド率か低い炉心下部の方が中性子
減速効果が大きく、反応度が高く、従って出力が高くな
るので、下部領域の可燃性毒物を多くすることは、サイ
クル初期の下方の出力ピークを抑え、ひいては燃料の運
転制限値である最大線出力密度を設計基準内に収めてお
くことができる。In a BWR, the lower part of the core with a lower void fraction generally has a greater neutron moderation effect, higher reactivity, and therefore higher output, so increasing the amount of burnable poison in the lower part reduces the lower output peak at the beginning of the cycle. Therefore, the maximum linear power density, which is the fuel operating limit value, can be kept within the design standard.
ところが、このような可燃性毒物分布を与えた場合、サ
イクルを通じて殆どの期間、炉心下部の出力を抑えた軸
方向出力分布で燃焼することになり、炉心反応度の増加
が期待できない。However, if such a burnable poison distribution is provided, the fuel will burn in an axial power distribution that suppresses the power in the lower part of the core for most of the cycle, and no increase in core reactivity can be expected.
これとは逆に、サイクル初期からサイクル中期にかけて
炉心下方ピークとすれば、この効果が期待できる。On the contrary, this effect can be expected if the peak is made below the core from the beginning of the cycle to the middle of the cycle.
すなわち、サイクル初期からサイクル中期にかけて軸方
向出力分布が下方ピークとなり、炉心の平均ボイド率が
高くなると、中性子スペクトルが硬くなり、プルトニウ
ムＰｕの蓄積を図ることができ、炉心反応度を増加させ
ることができる。また、サイクル末期では、可燃性毒物
が燃え尽きること、サイクル初期からサイクル中期まで
下部領域の燃焼が進むこと、および前記の濃縮度分布が
下部領域に比べ上部領域を高くしていることがら炉心軸
方向分布が上部ピークとなる。In other words, when the axial power distribution reaches a downward peak from the beginning of the cycle to the middle of the cycle and the average void fraction of the core increases, the neutron spectrum becomes harder, making it possible to accumulate plutonium (Pu) and increase the core reactivity. can. In addition, at the end of the cycle, burnable poisons burn out, combustion progresses in the lower region from the beginning of the cycle to the middle of the cycle, and the enrichment distribution described above makes the upper region higher than the lower region. The distribution has an upper peak.
これにより炉心平均ボイド率が低くなり、炉心反応度を
増加させることができる。As a result, the core average void fraction can be lowered, and the core reactivity can be increased.
また、この燃料棒の効果により冷温時における炉心反応
度を下げることができるので、炉停止余裕を改善するこ
とができる。Furthermore, the effect of these fuel rods makes it possible to lower the reactor core reactivity at cold temperatures, thereby improving reactor shutdown margin.
本発明の燃料集合体においては、サイクル初期の下方ピ
ークは全体的に可燃性毒物が多い下部領域で抑え、かつ
、下部領域に濃度が薄い可燃性毒物を１〜２本配置して
いるので、この可燃性毒物が燃え尽きた後のサイクル初
期を過ぎた時点より下方ピークとし、サイクル末期での
炉心反応度を得ることができる。In the fuel assembly of the present invention, the downward peak at the beginning of the cycle is suppressed in the lower region where there is a large amount of burnable poison as a whole, and one or two burnable poisons with a low concentration are placed in the lower region. The lower peak is obtained after the early stage of the cycle after this burnable poison has been burned out, and the core reactivity at the end of the cycle can be obtained.
（実施例）
次に、第１図ないし第３図を参照して本発明の燃料集合
体の実施例を説明する。(Example) Next, an example of the fuel assembly of the present invention will be described with reference to FIGS. 1 to 3.
本実施例の燃料集合体１０は、多数本の燃料棒２０と、
それらの中心に形成されたウォータロッド２１と、これ
らを収容するチャンネルボックス２２とから構成されて
いる。また、燃料集合体１０には、下部タイブレート、
上部タイブレートおよびスペーサ（いずれも図示せず）
が取付けられている。The fuel assembly 10 of this embodiment includes a large number of fuel rods 20,
It is composed of a water rod 21 formed at the center thereof and a channel box 22 that accommodates the water rod 21. The fuel assembly 10 also includes a lower tie plate,
Upper tie plate and spacer (both not shown)
is installed.
燃料棒２０およびウォータロッド２１の上下端部は、上
部タイブレートおよび下部タイブレートによって保持さ
れている。スペーサは燃料棒２０の軸方向にいくつか配
置され、燃料棒２０およびウォータロッド２１の相互間
の間隙を適切な状態に保持している。また、上部タイブ
レートにはチャンネルファスナ（図示せず）が取付けら
れている。The upper and lower ends of the fuel rod 20 and the water rod 21 are held by an upper tie plate and a lower tie plate. Several spacers are arranged in the axial direction of the fuel rods 20, and maintain an appropriate gap between the fuel rods 20 and the water rods 21. Additionally, a channel fastener (not shown) is attached to the upper tie plate.
燃料棒２０は、図示されていない下部端栓および上部端
栓にて両端を密封された被覆管内に多数の燃料ペレット
を装荷したものである。The fuel rod 20 has a large number of fuel pellets loaded in a cladding tube whose both ends are sealed with a lower end plug and an upper end plug (not shown).
燃料ペレットは燃料物質である二酸化ウランＵＯ２にて
構成され、核分裂物質であるウラン２３５を含んでいる
。また、被覆管内のガスブレナム内にはスプリングか配
置され、燃料ペレットを下方に押圧している。The fuel pellets are composed of uranium dioxide UO2, which is a fuel material, and contain uranium-235, which is a fissile material. Additionally, a spring is placed within the gas blemish within the cladding tube to press the fuel pellets downward.
ウォータロッド２１は燃料棒２０と同し材質の被覆管で
構成されているか、燃料物質を装荷しておらず、被覆管
（図示せず）の上部および下部の側面に孔を透設され、
内部を沸騰しない冷却材が通過する構造とされている。The water rod 21 is made of a cladding tube made of the same material as the fuel rod 20, or is not loaded with fuel material, and has holes formed in the upper and lower sides of the cladding tube (not shown).
It has a structure in which a non-boiling coolant passes through the inside.
ＢＷＲの炉心には、４体の燃料集合体１０に対して１体
の割合いで、横断面十字型の制御棒３０が挿入されてい
る。A control rod 30 having a cross-shaped cross section is inserted into the core of a BWR at a ratio of one control rod for every four fuel assemblies 10.
この炉心には、挿入される制御棒３０に面する燃料集合
体１０の側壁側に形成された水ギャップの幅が、その反
対側にあって制御棒３０に面しない燃料集合体１０の側
壁側に形成された水ギャップの幅よりも広くなっている
炉心（Ｄ格子炉心）と、制御棒３０に面する燃料集合体
１０の側壁側に形成された水ギャップの幅が、その反対
側にあって制御棒３０に面しない燃料集合体１０の側壁
側に形成された水ギャップの幅と等しい炉心（Ｃ格子炉
心）とがある。In this core, the width of the water gap formed on the side wall side of the fuel assembly 10 facing the control rods 30 to be inserted is the same as that on the side wall side of the fuel assembly 10 that is opposite to the side wall side facing the control rods 30. The width of the water gap formed in the core (D lattice core) is wider than the width of the water gap formed on the side of the fuel assembly 10 facing the control rods 30 on the opposite side. There is a core (C lattice core) having a width equal to the width of the water gap formed on the side wall side of the fuel assembly 10 that does not face the control rods 30.
本実施例の燃料集合体１０は、上記Ｃ格子炉心に装荷さ
れる燃料集合体である。The fuel assembly 10 of this embodiment is a fuel assembly loaded into the C-lattice core.
燃料集合体１０を構成する燃料棒２０には、第１図に示
すように、燃料棒１１〜１８の８種類がある。これらの
燃料棒１１〜１８が、第１図のようにチャンネルボック
ス２２内の燃料集合体横断面に配置されている。As shown in FIG. 1, there are eight types of fuel rods 20 constituting the fuel assembly 10: fuel rods 11 to 18. These fuel rods 11 to 18 are arranged in the cross section of the fuel assembly within the channel box 22 as shown in FIG.
本実施例におけるウォータロッド２１の口径は第１図の
ように、４本の燃料棒２０の領域を占領する大きさとさ
れ、燃料集合体１０の横断面中央に位置している。The diameter of the water rod 21 in this embodiment is set to be large enough to occupy the area of the four fuel rods 20, as shown in FIG. 1, and is located at the center of the cross section of the fuel assembly 10.
これにより水対燃料費が従来燃料より大きくなり、高燃
焼度化による炉心特性の悪化を解決し、同時に反応度の
向上をはかっている。This increases the water-to-fuel cost compared to conventional fuels, solves the deterioration of core characteristics caused by high burnup, and at the same time improves reactivity.
燃料棒２０を構成する８種の燃料棒１１〜１８には、燃
料物質充填領域の下端部および上端部に天然ウランから
なる燃料ペレットを充填した天然ウランブラケット領域
ＮＩ ＳＮ２が形成されている。In the eight types of fuel rods 11 to 18 constituting the fuel rod 20, natural uranium bracket regions NI SN2 filled with fuel pellets made of natural uranium are formed at the lower and upper ends of the fuel material filling region.
これらの天然ウランブラケットＮｌ 、Ｎ２は、第２図
に示すように、燃料物質充填領域の下端０及び上端２４
からそれぞれ燃料物質充填領域の軸方向の長さ（以下、
有効燃料長Ｈという）の１／２４の位置までを占めてい
る。These natural uranium brackets Nl, N2 are located at the lower end 0 and at the upper end 24 of the fuel material filling area, as shown in FIG.
to the axial length of the fuel material filling area (hereinafter referred to as
It occupies up to 1/24th of the effective fuel length H (referred to as effective fuel length H).
なお、燃料物質充填領域は、燃料ペレットを充填してい
る領域を意味し、各燃料棒１１〜１８の燃料物質充填領
域の軸方向の長さは等しい。また各燃料棒において、燃
料物質充填領域の下端から燃料有効長Ｈの１／２４〜２
３／２４の範囲は濃縮ウランか充填されている濃縮ウラ
ン領域Ｃである。Note that the fuel material filling region means a region filled with fuel pellets, and the length of the fuel material filling region of each of the fuel rods 11 to 18 in the axial direction is equal. In addition, in each fuel rod, 1/24 to 2 of the effective fuel length H from the lower end of the fuel material filling area.
The range of 3/24 is enriched uranium region C, which is filled with enriched uranium.
第２図に示すように燃料棒１１．１３．１６．１７およ
び１８ては、濃縮ウラン領域Ｃが軸方向において−様な
濃縮度になっており、また、燃料棒１２．１４および１
５では、濃縮ウラン領域が軸方向で濃縮度の異なる３つ
の領域ＣＩ ＳＣ２、Ｃ３から構成されている。As shown in FIG. 2, in the fuel rods 11, 13, 16, 17 and 18, the enriched uranium region C has a -like enrichment in the axial direction, and the fuel rods 12, 14 and 1
In No. 5, the enriched uranium region is composed of three regions CI SC2 and C3 with different degrees of enrichment in the axial direction.
各燃料棒の濃縮ウラン領域の濃縮度は、燃料棒１１で４
．３重量％、燃料棒１３．１６．１７および１８て、３
．３重量％になっている。The enrichment level in the enriched uranium region of each fuel rod is 4 in fuel rod 11.
．． 3% by weight, fuel rods 13.16.17 and 18, 3
．． It is 3% by weight.
燃料棒１２は、濃縮ウラン領域において、燃料物質充填
領域の下端を基点として燃料有効長Ｈの１７２４〜１０
／２４の範囲の濃縮度ｃｉが３．３重量％、燃料有効長
Ｈの１０７２４〜２０／２４の範囲Ｃ２の濃縮度カ３．
８％重量、燃料有効長Ｈ（７） ２０／２４〜２３／２
４の範囲の濃縮度Ｃ３が３．３重量％である。In the enriched uranium region, the fuel rod 12 has an effective fuel length H of 1724 to 10
The enrichment ci in the range of /24 is 3.3% by weight, and the enrichment ci in the range C2 of the fuel effective length H from 10724 to 20/24 is 3.3% by weight.
8% weight, fuel effective length H (7) 20/24~23/2
The concentration C3 in the range of 4 is 3.3% by weight.
同様に、燃料棒１４では、Ｃ１−２，９、Ｃ２−３，３
、Ｃ３−２，９重量％であり、燃料棒１５ではＣ１−２
，１、Ｃ２−２，５、Ｃ３−２，１重量％である。Similarly, in the fuel rod 14, C1-2,9, C2-3,3
, C3-2.9% by weight, and in fuel rod 15, C1-2
, 1, C2-2,5, C3-2,1% by weight.
燃料棒１６．１７．１８は濃縮ウラン領域の燃料ペレッ
ト内に可燃性毒物であるガドリニアを含有している。Fuel rods 16, 17, 18 contain gadolinia, a burnable poison, within the fuel pellets in the enriched uranium region.
燃料棒１６における濃縮ウラン領域の軸方向におけるガ
ドリニア濃度は、燃料物質充填領域の下端を基点として
燃料有効長Ｈのｌ／２４〜Ｉ Ｏ／２４の範囲テ５．０
重量％、燃料有効長Ｈ（７） １０／２４〜２０／２４
の範囲で４．０重量％、２０／２４〜２３／２４の範囲
で３．０重量％である。The gadolinia concentration in the axial direction of the enriched uranium region in the fuel rod 16 is within the range of l/24 to I O/24 of the effective fuel length H, starting from the lower end of the fuel material filling region.
Weight %, fuel effective length H (7) 10/24~20/24
4.0% by weight in the range of 20/24 to 23/24, and 3.0% by weight in the range of 20/24 to 23/24.
燃料棒１７のガドリニア濃度は、燃料物質充填領域の下
端を基点として、燃料有効長Ｈの１／２４〜２０／２４
の範囲テ４．０重量％、燃料有効長Ｈの２ｏ／２４〜２
３／２４の範囲で８．０重量％である。The gadolinia concentration of the fuel rod 17 is 1/24 to 20/24 of the effective fuel length H, with the lower end of the fuel material filling region as the base point.
range Te 4.0% by weight, fuel effective length H 2o/24~2
It is 8.0% by weight in the range of 3/24.
本発明の特徴をなす燃料棒１８のガドリニア濃度は、燃
料有効長Ｈの１／２４〜１０／２４ （７）範囲テ２．
０重量％、１０／２４〜２０／２４の範囲テ４．０重量
％、２゜／２４〜２３／２４の範囲で３．０重量％であ
る。The gadolinia concentration of the fuel rod 18, which is a feature of the present invention, is within the range of 1/24 to 10/24 of the effective fuel length H (7) 2.
0% by weight, 4.0% by weight in the range of 10/24 to 20/24, and 3.0% by weight in the range of 2°/24 to 23/24.
なお、燃料棒１１〜１５は、ガドリニアを含有していな
い。Note that the fuel rods 11 to 15 do not contain gadolinia.
上記のような軸方向濃縮度分布を有する燃料棒１１〜１
８を第１図のように配置することによって、燃料集合体
１０の軸方向における各部の断面平均濃縮度分布は第２
図の右端に示すように、燃料集合体の燃料物質充填領域
の下端を基点として燃料有効長Ｈ（７）ｌ／２４〜１０
／２４ ノ範囲ＣＩ（ａ縮つラン領域の下部領域）およ
び燃料有効長Ｈの２０／２４〜２３／２４の範囲（濃縮
ウラン領域の上部領域）で３．４４重量％、燃料有効長
Ｈの１ｏ／２４〜２ｏ／２４ノ範囲（濃縮ウラン領域の
中央部領域）で３．６４重量％となる。また、燃料物質
充填領域の上下端部に形成される天然ウランブランケッ
ト領域Ｎｌ 、Ｎ２は０．７１重量％のウラン２３５を
含有している。Fuel rods 11-1 having the above-described axial enrichment distribution
8 as shown in FIG. 1, the cross-sectional average enrichment distribution of each part in the axial direction of the fuel assembly 10 becomes the second
As shown at the right end of the figure, the effective fuel length H(7) l/24 to 10 from the lower end of the fuel material filling area of the fuel assembly
3.44% by weight in the 20/24 to 23/24 range of the fuel effective length H (upper region of the enriched uranium region), It is 3.64% by weight in the range of 1o/24 to 2o/24 (center region of enriched uranium region). Further, the natural uranium blanket regions Nl and N2 formed at the upper and lower ends of the fuel material filling region contain 0.71% by weight of uranium-235.
本実施例における燃料集合体は、濃縮ウラン領域の下部
領域Ｃ１の断面平均濃縮度を低くし、濃縮ウラン領域の
中央部領域Ｃ２の断面平均濃縮度を高くし、それらの領
域の間で約０．２重量９６の平均濃縮度差をつけている
。In the fuel assembly in this example, the cross-sectional average enrichment of the lower region C1 of the enriched uranium region is made low, the cross-sectional average enrichment of the central region C2 of the enriched uranium region is made high, and there is a gap between these regions of about 0. There is an average concentration difference of .2 weight 96.
ＢＷＲでは炉心上端に行くに従って蒸気泡（ボイド）が
多いため、炉心上部で中性子減速材であろ水の密度が低
下する。このため、軸方向の濃縮度分布が−様な燃料集
合体を炉心内に装荷した場合には、燃料集合体下部に出
力ピークが生ずる下歪みの出力分布となる傾向がある。In a BWR, there are more steam bubbles (voids) toward the top of the core, so the density of water, which is a neutron moderator, decreases at the top of the core. For this reason, when a fuel assembly with a −-like axial enrichment distribution is loaded into a reactor core, the output distribution tends to be downwardly distorted with an output peak occurring at the bottom of the fuel assembly.
従って、前述のように、燃料集合体の下部領域よりも中
央部領域の濃縮度を高くすることによって、燃料集合体
の軸方向の出力分布を平坦化することができる。Therefore, as described above, by making the enrichment level higher in the central region than in the lower region of the fuel assembly, the power distribution in the axial direction of the fuel assembly can be flattened.
本実施例の燃料集合体における中央部領域ｃ２と下部領
域Ｃ１との平均濃縮度の差、約０．２重量％と、中央部
領域ｃ２および下部領域ｃ１の境界位置（燃料有効長Ｈ
の１０７２４の位置）は、軸方向出力分布平坦化の効果
が最大となるよう選んだものである。The difference in average enrichment between the central region c2 and the lower region C1 in the fuel assembly of this example is approximately 0.2% by weight, and the boundary position (fuel effective length H) between the central region c2 and the lower region c1
10724) is selected so that the effect of flattening the axial output distribution is maximized.
本実施例における燃料集合体２ｏの内、１０本のガドリ
ニア入り燃料棒１６．１７のガドリニアの平均重量％は
、第２図および第３図に示すように、全体的には下部領
域を高くして中央部領域を低くし、それらの領域の間で
約０．５重量％の差をつけている。As shown in FIGS. 2 and 3, the average weight percent of gadolinia in the 10 gadolinia-containing fuel rods 16.17 in the fuel assembly 2o in this example is such that the lower region is higher overall. The central region is lowered, with a difference of about 0.5% by weight between the regions.
前述のように、ＢＷＲでは炉心上端に行くに従ってボイ
ドが多いため、炉心上部では中性子減速材である水の密
度が低く、炉心下部では水の密度が高い。このため軸方
向のガドリニア平均重量％を同一とすると、炉心下部で
中性子スペクトルが上部に比べて軟らかいことから、ガ
ドリニアの燃焼が早く進む。これによりガドリニアの燃
焼が進む際の炉心下部の反応度の上昇速度か早くなるた
め、軸方向の出力分布が下部ピークとなり易くなる。As mentioned above, in a BWR, the number of voids increases toward the top of the core, so the density of water, which is a neutron moderator, is low in the top of the core, and the density of water is high in the bottom of the core. For this reason, if the average weight percent of gadolinia in the axial direction is the same, the neutron spectrum is softer in the lower part of the core than in the upper part, so the combustion of gadolinia proceeds faster. As a result, the rate of increase in the reactivity in the lower part of the core as the combustion of gadolinia progresses becomes faster, making it easier for the axial power distribution to peak at the lower part.
本発明では、これを適切に゛制御するため、下部領域に
おけるガドリニアの平均濃度を０．５重量％大きくして
いる。この濃度差０．５重量％は軸方向出力分布の平坦
化の効果が最適となるように選んだものである。In the present invention, in order to appropriately control this, the average concentration of gadolinia in the lower region is increased by 0.5% by weight. This concentration difference of 0.5% by weight was selected so that the effect of flattening the axial power distribution would be optimal.
なお、この実施例では、ガドリニア入り燃料棒が３種類
あるが、これは燃料製造上の配慮からであり、同−燃料
内でガドリニアの濃度の差を約１重量％以上とするため
である。In this example, there are three types of gadolinia-containing fuel rods, but this is due to consideration in fuel production, and is to ensure that the difference in gadolinia concentration within the same fuel is approximately 1% by weight or more.
更に本発明では、ガドリニア入り燃料棒１８の下部領域
のガドリニアの平均重量を２．０重量％と中央部領域の
４．０重量％よりも低くし、サイクル初期の軸方向の出
力分布が下部ピークとなるのを押えた後、下部領域のガ
ドリニアが燃焼した後のサイクル中期以降に適度な下部
ピークとなるようにして、炉心反応度を得ている。Furthermore, in the present invention, the average weight of gadolinia in the lower region of the gadolinia-containing fuel rod 18 is set to 2.0% by weight, which is lower than 4.0% by weight in the central region, so that the axial power distribution at the beginning of the cycle has a lower peak. After suppressing this, the core reactivity is obtained by achieving a moderate lower peak after the middle of the cycle after the gadolinia in the lower region has been burned.
このような選択によって得られた軸方向の濃縮度分布お
よびガドリニア濃度差によって生じる燃料集合体の出力
ビーキングの余裕は約１５％〜２０％となる。本発明の
燃料集合体では、この出力ビーキングの余裕を高燃焼度
化によるピーキングの増加の緩和および前述のような反
応度利得に振向けて燃料経済性を向上させている。The power peaking margin of the fuel assembly caused by the axial enrichment distribution and gadolinia concentration difference obtained by such selection is about 15% to 20%. In the fuel assembly of the present invention, the margin of output peaking is used to alleviate the increase in peaking due to higher burnup and to gain the reactivity as described above, thereby improving fuel economy.
なお、第３図にも示すように、燃料集合体における濃縮
ウラン領域の上部領域Ｃ３（燃料有効長Ｈの２０７２４
〜２３／２４）の断面平均濃縮度は、下部領域ＣＩ（燃
料有効長Ｈのｌ／２４〜１０／２４ ）の断面平均濃縮
度とほぼ等しく低濃縮度領域であり、かつ燃料棒１６．
１７の可燃性毒物の低濃度領域に対応しており、炉停止
余裕の減少を補償している。また、濃縮ウラン領域の上
部領域の軸方向長さ（燃料有効長Ｈの３７２４）は、可
燃性毒物減少による経済的効果が最大となるよう決定し
たものである。As shown in FIG. 3, the upper region C3 of the enriched uranium region in the fuel assembly (20724
The cross-sectional average enrichment of the fuel rods 16. to 23/24) is approximately equal to the cross-sectional average enrichment of the lower region CI (1/24 to 10/24 of the fuel effective length H), and is a low enrichment region.
It corresponds to the low concentration range of 17 burnable poisons and compensates for the reduction in reactor shutdown margin. Further, the axial length of the upper region of the enriched uranium region (3724 of the fuel effective length H) was determined so as to maximize the economic effect of reducing burnable poisons.
以上述べたように、本発明の燃料集合体によれば、燃料
経済性を著しく向上できる。As described above, according to the fuel assembly of the present invention, fuel economy can be significantly improved.
即ち、本発明の燃料集合体は、原子炉の安全余裕を十分
確保しつつ、可能な限り低い濃縮度で、目標とする高燃
焼度を達成することができ、これによって燃料サイクル
に要する費用を著しく低減できる。また使用済み燃料集
合体の発生量も著しく低減することができる。In other words, the fuel assembly of the present invention can achieve the target high burnup at the lowest possible enrichment while ensuring a sufficient safety margin for the reactor, thereby reducing the cost required for the fuel cycle. It can be significantly reduced. Furthermore, the amount of spent fuel assemblies generated can be significantly reduced.
［発明の効果］
本発明によれば、高燃焼度化による炉心性能の悪化を解
消すると共に、出力ビーキングの余裕を燃料経済性の向
上に利用でき、取出しエネルギーを著しく増大できる。[Effects of the Invention] According to the present invention, deterioration in core performance due to high burnup can be eliminated, and margin of power peaking can be used to improve fuel economy, and extraction energy can be significantly increased.
第１図は本発明の実施例である燃料集合体の横断面図、
第２図は第１図に示す燃料集合体を構成する燃料棒の濃
縮度およびガドリニア分布を示す説明図、第３図は本発
明の燃料集合体を構成する濃縮度および可燃性毒物の分
布を示す模式図である。
１０・・・・・・・・・燃料集合体
２０（１１〜１８）・・・燃料棒
２１・・・・・・・・・ウォーターロッド２２・・・・
・・・・チャンネルボックス３０・・・・・・・・・制
御棒FIG. 1 is a cross-sectional view of a fuel assembly that is an embodiment of the present invention;
Fig. 2 is an explanatory diagram showing the enrichment and gadolinia distribution of the fuel rods constituting the fuel assembly shown in Fig. 1, and Fig. 3 shows the enrichment and the distribution of burnable poisons constituting the fuel assembly of the present invention. FIG. 10...Fuel assembly 20 (11-18)...Fuel rod 21...Water rod 22...
...Channel box 30... Control rod
Claims (1)
集合体において、この燃料集合体の軸方向の領域に関し
、上部領域と比べ下部領域の可燃性毒物の平均含有量を
多くし、かつその内１〜２本の燃料棒の下部領域におけ
る単位長さ、燃料棒当りの可燃性毒物の含有量を上部領
域よりも少なくしたことを特徴とする燃料集合体。In a fuel assembly having a plurality of fuel rods filled with fuel material inside, the average content of burnable poison is increased in the lower region in the axial direction of the fuel assembly than in the upper region, and A fuel assembly characterized in that the unit length of one or two of the fuel rods in the lower region and the content of burnable poison per fuel rod are smaller than in the upper region.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2067875A JP2966877B2 (en) | 1990-03-15 | 1990-03-15 | Fuel assembly |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2067875A JP2966877B2 (en) | 1990-03-15 | 1990-03-15 | Fuel assembly |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH03267793A true JPH03267793A (en) | 1991-11-28 |
| JP2966877B2 JP2966877B2 (en) | 1999-10-25 |
Family
ID=13357530
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2067875A Expired - Lifetime JP2966877B2 (en) | 1990-03-15 | 1990-03-15 | Fuel assembly |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2966877B2 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2014048159A (en) * | 2012-08-31 | 2014-03-17 | Hitachi-Ge Nuclear Energy Ltd | Fuel assembly and nuclear reactor core |
| WO2022061689A1 (en) * | 2020-09-25 | 2022-03-31 | 中广核研究院有限公司 | Burnable poison rod and fuel assembly containing burnable poison rod |
-
1990
- 1990-03-15 JP JP2067875A patent/JP2966877B2/en not_active Expired - Lifetime
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2014048159A (en) * | 2012-08-31 | 2014-03-17 | Hitachi-Ge Nuclear Energy Ltd | Fuel assembly and nuclear reactor core |
| WO2022061689A1 (en) * | 2020-09-25 | 2022-03-31 | 中广核研究院有限公司 | Burnable poison rod and fuel assembly containing burnable poison rod |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2966877B2 (en) | 1999-10-25 |
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