JPH0481695A - Core of fast reactor - Google Patents
Core of fast reactorInfo
- Publication number
- JPH0481695A JPH0481695A JP2194789A JP19478990A JPH0481695A JP H0481695 A JPH0481695 A JP H0481695A JP 2194789 A JP2194789 A JP 2194789A JP 19478990 A JP19478990 A JP 19478990A JP H0481695 A JPH0481695 A JP H0481695A
- Authority
- JP
- Japan
- Prior art keywords
- fuel
- reactor
- coolant
- core
- reactivity
- 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.)
- Pending
Links
- 239000000446 fuel Substances 0.000 claims abstract description 160
- 239000002826 coolant Substances 0.000 claims abstract description 62
- 230000000712 assembly Effects 0.000 claims abstract description 27
- 238000000429 assembly Methods 0.000 claims abstract description 27
- 239000011800 void material Substances 0.000 claims description 17
- 230000009257 reactivity Effects 0.000 abstract description 24
- 230000007423 decrease Effects 0.000 description 6
- 239000008188 pellet Substances 0.000 description 6
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 4
- 238000009835 boiling Methods 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 229910052708 sodium Inorganic materials 0.000 description 4
- 239000011734 sodium Substances 0.000 description 4
- 230000002093 peripheral effect Effects 0.000 description 3
- 239000000463 material Substances 0.000 description 2
- 230000007704 transition Effects 0.000 description 2
- 229910052580 B4C Inorganic materials 0.000 description 1
- 241001494479 Pecora Species 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 239000006096 absorbing agent Substances 0.000 description 1
- 230000002238 attenuated effect Effects 0.000 description 1
- INAHAJYZKVIDIZ-UHFFFAOYSA-N boron carbide Chemical compound B12B3B4C32B41 INAHAJYZKVIDIZ-UHFFFAOYSA-N 0.000 description 1
- 244000309466 calf Species 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 230000007717 exclusion Effects 0.000 description 1
- 230000000977 initiatory effect Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000003758 nuclear fuel Substances 0.000 description 1
- 239000012857 radioactive material Substances 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 239000010959 steel 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
- Fuel-Injection Apparatus (AREA)
Abstract
Description
【発明の詳細な説明】
〔発明の目的〕
（産業上の利用分野）
本発明は冷却材密度係数ないしボイド係数か正値を採る
領域と、負値を採る領域とを有する高速増殖炉等の高速
炉炉心に係り、特に、万一、事故により冷却材の炉心流
量か減少したときに自然の原理で炉停止させる高速炉炉
心に関する。[Detailed Description of the Invention] [Object of the Invention] (Field of Industrial Application) The present invention is directed to a fast breeder reactor, etc., which has a region where the coolant density coefficient or void coefficient takes a positive value and a region where it takes a negative value. The present invention relates to fast reactor cores, and particularly relates to fast reactor cores that shut down the reactor using natural principles in the event that the core flow rate of coolant decreases due to an accident.
（従来の技術）
一般に、高速炉炉心では、極低度事象、つまり、発生頻
度か１０〜１０”／炉年の極めて低確率であるために工
学的には殆ど発生するとは考えられない事象が発生した
場合でも、放射性物質を環境に放比させないための対策
か種々施されている。(Prior art) In general, in fast reactor cores, very low-level events, that is, events that occur with an extremely low probability of occurrence of 10 to 10 inches per reactor year, are hardly considered to occur from an engineering standpoint. Even in the event of an outbreak, various measures are being taken to prevent radioactive materials from being released into the environment.
（発明か解決しようとする課題）
しかしながら、このような従来の高速炉炉心ではこのよ
うな極低度事象が発生した場合、その事故影響は原子炉
容器内に止めることができるものの、炉心燃料全体に亘
る損傷か生ずる可能性かある。(Problem to be solved by the invention) However, when such an extremely low-intensity event occurs in a conventional fast reactor core, although the effects of the accident can be contained within the reactor vessel, the entire core fuel is There is a possibility that damage may occur.
次に、この極低度事象の一例として、流量減少時の炉停
止失敗事象について、その発生から燃料損傷に至るまで
の経過を説明する。Next, as an example of this extremely low-level event, a description will be given of a failure to shut down the reactor when the flow rate decreases, and the progress from its occurrence to fuel damage.
（１）まず、何等かの起因事象の発生により、高速炉の
一次主循環ポンプがトリップし、しかも、それにも拘ら
ず炉停止系の不動作によって炉停止できない場合はナト
リウム等の冷却材炉心流量か低下するので、炉心燃料に
おける出力−流量不整合により、冷却材温度か上昇する
。(1) First, if the primary main circulation pump of the fast reactor trips due to the occurrence of some initiating event, and the reactor cannot be shut down due to the inoperation of the reactor shutdown system, the core flow rate of coolant such as sodium As the temperature decreases, the coolant temperature increases due to the power-flow mismatch in the core fuel.
（２）冷却材温度か上昇する過程において炉停止できな
い場合は、冷却材か遂に沸騰し、ナトリウムボイド反応
が挿入され、ボイド反応度か正値であった場合は、炉出
力か上昇する可能性がある。(2) If the reactor cannot be stopped while the coolant temperature is rising, the coolant will finally boil and a sodium void reaction will be inserted, and if the void reactivity is a positive value, there is a possibility that the reactor output will increase. There is.
（３）この炉出力上昇により、炉心燃料の燃料ペレット
の温度上昇が炉心全体に行き亘ると、燃料損傷が生ずる
可能性が発生する。(3) Due to this increase in reactor power, if the temperature of the fuel pellets of the reactor fuel spreads throughout the reactor core, there is a possibility that fuel damage will occur.
そこで本発明は前記事情を考慮してなされたもので、そ
の目的は万一、炉停止に失敗し、原子炉スクラム動作か
不能となるような極低度事象か発生した場合においても
、炉心全体に燃料損傷か及ぶことを未然に防止して炉停
止することができる高速炉炉心を提供することにある。Therefore, the present invention was made in consideration of the above circumstances, and its purpose is to prevent the entire reactor core from being damaged even if an extremely low-level event occurs, such as failing to shut down the reactor and disabling reactor scram operation. An object of the present invention is to provide a fast reactor core that can shut down the reactor while preventing fuel damage from occurring.
（課題を解決するための手段）
本発明は前記課題を解決するために次のように構成され
る。(Means for Solving the Problems) In order to solve the above problems, the present invention is configured as follows.
つまり本発明は、複数本の燃料要素を冷却材が通液自在
に内蔵する複数の燃料集合体を装荷して、冷却材密度係
数ないしボイド係数が負値をなす領域を有する高速炉炉
心において、前記冷却材密度係数ないしボイド係数か負
値をなす領域にある前記燃料集合体の少なくとも一部を
、その出力／流量比か他の前記燃料集合体のものよりも
大きい先行燃料集合体に構成したことを特徴とする。In other words, the present invention provides a fast reactor core loaded with a plurality of fuel assemblies containing a plurality of fuel elements through which coolant can freely flow, and which has a region where the coolant density coefficient or void coefficient takes a negative value. At least a portion of the fuel assemblies in a region where the coolant density coefficient or void coefficient has a negative value is configured as a leading fuel assembly whose power/flow ratio is larger than that of the other fuel assemblies. It is characterized by
（作用）
何等かの原因により例えば高速炉の一次主循環ポンプが
トリップしたにも拘らず、炉停止系の不動作によって原
子炉スクラムできないという炉停止失敗事象が生じると
、この炉心流量の減少により先行燃料集合体はその内部
を通液する冷却材温度上昇を他の燃料集合体に先駆けて
先行的に上昇させ、その温度上昇量を増大させる。(Function) If a reactor shutdown failure event occurs, in which the reactor cannot scram due to the inoperation of the reactor shutdown system, even though the primary main circulation pump of the fast reactor trips due to some reason, this decrease in core flow rate causes The leading fuel assembly increases the temperature of the coolant flowing through it in advance of other fuel assemblies, thereby increasing the amount of temperature rise.
この先行燃料集合体がある領域では冷却材密度係数ない
しボイド係数が負値であるので、この先行燃料集合体に
おける冷却材温度上昇は他の燃料集合体よりも大きいた
めに負反応度が先行的に挿入される。Since the coolant density coefficient or void coefficient is a negative value in the area where this preceding fuel assembly exists, the coolant temperature rise in this preceding fuel assembly is larger than that in other fuel assemblies, so the negative reactivity is higher than that in the preceding fuel assembly. inserted into.
このために、炉出力が低減し、原子炉が炉停止状態に移
行し、全炉心に亘る燃料損傷か未然に防止される。For this reason, the reactor power is reduced, the reactor enters a reactor shutdown state, and fuel damage to the entire reactor core is prevented.
また、万一、冷却材が沸騰した場合は、この沸騰は先行
燃料集合体で選択的かつ先行的に発生するので、負の冷
却材ボイド反応度に起因して負の反応度が挿入され、そ
のために炉出力が低減していき、原子炉が炉停止状態に
移行し、その結果、全炉心に亘る燃料損傷が未然に防止
される。In addition, in the event that the coolant boils, this boiling occurs selectively and proactively in the preceding fuel assembly, so a negative reactivity is inserted due to the negative coolant void reactivity. As a result, the reactor power is reduced and the reactor enters a reactor shutdown state, thereby preventing fuel damage to the entire reactor core.
さらに、万一、燃料損傷が発生する場合は、これも先行
燃料集合体で選択的かつ先行的に生じ、しかも、その損
傷しあるいは溶融した燃料の一部はその外部に排除され
るので、その燃料排除に伴う負の反応度が挿入される。Furthermore, in the event that fuel damage occurs, this will also occur selectively and in advance in the preceding fuel assembly, and a portion of the damaged or melted fuel will be expelled to the outside. Negative reactivity due to fuel exclusion is inserted.
その結果、原子炉は炉停止状態に移行し、燃料損傷は先
行燃料集合体のみに限定され、燃料損傷が炉心全体に及
ぶのを未然に防止することかできス
（実施例）
以下本発明の実施例を第１図〜第６図に基づいて説明す
る。As a result, the reactor transitions to a reactor shutdown state, and fuel damage is limited to only the preceding fuel assembly, making it possible to prevent fuel damage from extending to the entire reactor core (Example). An embodiment will be described based on FIGS. 1 to 6.
第１図は本発明に係る高速炉炉心の一実施例の概略平面
図であり、図において、炉心１は冷却材密度係数ないし
ボイド係数か正値を採る領域である中央部に複数本の燃
料集合体２を複数本の制御棒３と共に配設し、その外周
には先行燃料集合体４、隣接燃料集合体５および中性子
遮蔽体６をこの順に順次配設し、これら２〜６をナトリ
ウム等の冷却材中に浸漬させている。FIG. 1 is a schematic plan view of an embodiment of a fast reactor core according to the present invention. In the figure, a core 1 has a plurality of fuels in the center, which is a region where the coolant density coefficient or void coefficient takes a positive value. An assembly 2 is arranged together with a plurality of control rods 3, and a preceding fuel assembly 4, an adjacent fuel assembly 5, and a neutron shield 6 are arranged in this order around the outer periphery of the assembly 2, and these 2 to 6 are filled with sodium, etc. It is immersed in a coolant.
燃料集合体２は複数の燃料ペレットを内蔵した燃料ピン
の複数本を束状に結束して、例えば六角筒状のラッパ管
内に冷却材が通液自在に内蔵しており、前記したように
炉心中央部と、この中央部からその周方向に例えば６０
°間隔で外周側に矩形状に突出するように配設されてい
る。The fuel assembly 2 has a plurality of fuel pins each containing a plurality of fuel pellets tied together into a bundle, for example, a hexagonal cylindrical wrapper tube in which a coolant can freely flow. For example, 60 mm from the center in the circumferential direction from the center.
They are arranged so as to protrude in a rectangular shape toward the outer periphery at intervals of .
また、燃料集合体２より外周側の外周部は冷却材密度係
数ないしボイド係数が負値を示す領域であり、ここに、
燃料集合体２の外周縁に沿って例えば１周するように先
行燃料集合体４を１列で配設し、さらに、この先行燃料
集合体４の外周縁に沿って例えば１周するように２列で
隣接燃料集合体５を配置し、そのさらに外周の炉心最外
周部には複数の中性子遮蔽体６を外形が例えば六角形を
なすように配設し、中性子か炉心外へリークするリーク
量の低減を図っている。In addition, the outer peripheral part on the outer peripheral side of the fuel assembly 2 is a region where the coolant density coefficient or void coefficient shows a negative value, and here,
The preceding fuel assemblies 4 are arranged in one row so as to go around the outer periphery of the fuel assembly 2, for example, once, and further, the preceding fuel assemblies 4 are arranged in one row so as to go around once around the outer periphery of the preceding fuel assembly 4. Adjacent fuel assemblies 5 are arranged in rows, and a plurality of neutron shields 6 are arranged at the outermost periphery of the core so that the outer shape is, for example, a hexagon, and the amount of neutrons leaking out of the core is determined. We are trying to reduce this.
先行燃料集合体４は第２図に示すように、例えば六角筒
状のラッパ管７の内部に、複数の燃料ピン８，８・・・
を束状に結束して燃料ピン束８ａに構成して内蔵してお
り、ラッパ管６内にナトリウム等の冷却材をその図中下
端の入口ノズル９ａから流入させて、図中開口上端９ｂ
から外部へ流出させ、各燃料ピン８の外周面を冷却材が
通液することにより熱交換するようになっている。As shown in FIG. 2, the preceding fuel assembly 4 has a plurality of fuel pins 8, 8, .
are bundled into a bundle of fuel pins 8a and built-in, and a coolant such as sodium is flowed into the wrapper tube 6 from the inlet nozzle 9a at the lower end in the figure, and the opening at the upper end 9b in the figure.
The coolant flows out from the fuel pins 8 to the outside, and the coolant passes through the outer peripheral surface of each fuel pin 8, thereby exchanging heat.
各燃料ピン８はその上部内部に例えば円柱状の複数の燃
料ペレット１０．１０・・・を内蔵すると共に、その下
部内にはガスプレナム１１を設けている。Each fuel pin 8 houses a plurality of, for example, cylindrical fuel pellets 10, 10, in its upper part, and has a gas plenum 11 in its lower part.
また、先行燃料集合体４は各燃料ピン８の図中上端より
上方のラッパ管７の上部内を中空部１２に構成し、後述
する燃料ピン８の破損時の破損を外部に排出し易いよう
になっている。In addition, the preceding fuel assembly 4 has a hollow portion 12 in the upper part of the trumpet tube 7 above the upper end of each fuel pin 8 in the figure, so that damage caused when the fuel pin 8 is broken, which will be described later, can be easily discharged to the outside. It has become.
そして、各先行燃料集合体４は入口ノズル９ａの口径を
縮径し、あるいは燃料ペレット１ｏ内に含有される核分
裂性物質の含有率を増大させる等により燃料ピン束８ａ
の出力（Ｐ、）と、そのラッパ管７内部を通液する冷却
材の流量ＣＦｉ ）との比が炉心全体の燃料集合体の全
８カ（Σｐｌ）と全炉心流量（ΣＦＪ）との比、つまり
、炉心燃料集合体に対する平均の出力−流量比に対し、
次の（１）式を満足するように設定されている。Each of the preceding fuel assemblies 4 is constructed by reducing the diameter of the inlet nozzle 9a or increasing the content of fissile material contained in the fuel pellets 1o.
The ratio of the output (P, ) to the flow rate of coolant flowing through the inside of the trumpet tube 7 (CFi) is the ratio of all eight fuel assemblies (Σpl) in the entire core to the total core flow rate (ΣFJ). , that is, for the average power-flow ratio for the core fuel assembly,
It is set to satisfy the following equation (1).
ｌ：先行燃料集合体４に付した添字
ｊ：燃料集合体２に付した添字（１を含む）
この（１）式中ｎ は下記の範囲の値を採る定数である
。l: Subscript attached to the preceding fuel assembly 4 j: Subscript attached to the fuel assembly 2 (including 1) In this formula (1), n is a constant having a value within the following range.
１、０≦ｎ ≦２．０ ・・・・・・ （２
）このようなｎ を設定した結果として、本実施例の炉
心１においては、炉心燃料集合体２，４゜５の出力−流
量比と燃料集合体本数のとの関係は例えば第３図で示す
出力−流量比スペクトルを採るように分布し、先行燃料
集合体４はその出力−流量比４ａの方が他の燃料集合体
２の出力−流量比２ａよりも大きい値を持つ一群を形成
している。1, 0≦n≦2.0 (2
) As a result of setting n in this manner, in the core 1 of this embodiment, the relationship between the power-flow rate ratio of the core fuel assemblies 2 and 4°5 and the number of fuel assemblies is as shown in FIG. 3, for example. The preceding fuel assemblies 4 form a group whose output-flow ratio 4a is larger than the output-flow ratio 2a of the other fuel assemblies 2. There is.
一方、隣接燃料集合体５はそのラッパ管内部に燃料ペレ
ットあるいはブラケット燃料、ボロンカーバイド（Ｂ４
Ｃ）等の中性子吸収体、スチール、ガス、冷却材のいず
れか等を配設している。On the other hand, the adjacent fuel assembly 5 has fuel pellets, bracket fuel, boron carbide (B4
A neutron absorber such as C), steel, gas, or a coolant is installed.
そして、これら隣接燃料集合体５・・・と先行燃料集合
体４・・・との境界線１３は、先行燃料集合体４を含む
炉心燃料集合体の体積で定義される平均半径より成る円
周を周期的に交差するように形成され、かつ先行燃料集
合体４と隣接燃料集合体５との相互幾何学的配置か設定
されている。The boundary line 13 between these adjacent fuel assemblies 5 and preceding fuel assemblies 4 is a circumference defined by the average radius defined by the volume of the core fuel assembly including the preceding fuel assembly 4. The fuel assemblies 4 and 5 are formed so as to intersect periodically, and the mutual geometric arrangement of the preceding fuel assembly 4 and the adjacent fuel assembly 5 is set.
このような先行燃料集合体４と隣接燃料集合体５との位
置関係により、炉心ｌにおける冷却材密度係数ないしボ
イド係数の炉心径方向分布は第４図に示すようになる。Due to the positional relationship between the preceding fuel assembly 4 and the adjacent fuel assembly 5, the distribution of the coolant density coefficient or void coefficient in the core radial direction in the core I becomes as shown in FIG.
つまり、冷却材密度係数ないしボイド係数は炉心１の中
心部に近い領域Ａて正値を示す場合かあり、また、炉心
燃料領域の外周部Ｂては負値を示す。In other words, the coolant density coefficient or void coefficient may take a positive value in the area A near the center of the core 1, and may take a negative value in the outer periphery B of the core fuel area.
さらに、この冷却材密度、ボイド両反応度係数が負値を
採る領域において、その絶対値が最大値を有する領域Ｃ
の近傍りには前記先行燃料集合体４・・・か配設されて
いる。Furthermore, in the region where both the coolant density and the void reactivity coefficient take negative values, the region C where the absolute value thereof is the maximum value is
The preceding fuel assembly 4 is disposed near the fuel assembly 4.
但し、このような配置において各先行燃料集合体４の一
体当りの冷却材密度係数の絶対値の平均値符号ＩＷ、Ｉ
がその他の燃料集合体の冷却材密度係数の絶対値の平均
値ＩＷ、ｌに対し、次の」
（３）式の関係を満すものとする。However, in such an arrangement, the average value of the absolute value of the coolant density coefficient per unit of each preceding fuel assembly 4 has the sign IW, I
It is assumed that the following equation (3) is satisfied with respect to the average value IW, l of the absolute value of the coolant density coefficient of the other fuel assemblies.
ｎ ΣＩＷ １〉ΣＩＷ、Ｉ ・−・・・（３）Ｊ
ｊ ｊ
ここで、Σ は先行燃料集合体４に対する和、Σ は先
行燃料集合体４以外の燃料集合体に対する和をそれぞれ
示す。n ΣIW 1〉ΣIW, I ・－・・・(3) J
j j Here, Σ represents the sum for the preceding fuel assembly 4, and Σ represents the sum for the fuel assemblies other than the preceding fuel assembly 4, respectively.
次に、本実施例の作用を説明するか、ここでは万−１原
子炉の電源喪失等により原子炉スクラム信号が発生して
冷却材ポンプがトリップしたにも拘らず、制御棒３が炉
心１内に挿入されないという極低度事象か発生した場合
について説明する。Next, we will explain the operation of this embodiment.In this case, even though the reactor scram signal was generated due to a loss of power to the reactor and the coolant pump tripped, the control rods 3 We will explain the case where an extremely low-level event occurs in which the device is not inserted into the device.
この場合は、冷却材の炉心流量の減少により、出力−流
量間の不整合か発生し、冷却材温度が上昇する。In this case, the decrease in the core flow rate of coolant causes a mismatch between power and flow rate, and the coolant temperature increases.
このために、各燃料集合体２． ４． ５においては冷
却材密度の減少により冷却材反応度か挿入される。For this purpose, each fuel assembly 2. 4. 5, coolant reactivity is inserted due to the decrease in coolant density.
ここで、炉心１全体に挿入される冷却材反応度Δρ は
次の（４）式で表わされる。Here, the reactivity Δρ of the coolant inserted into the entire core 1 is expressed by the following equation (4).
ΔＴ ・先行燃料集合体４（ｉ）における冷却材温度上
昇）
Ｗ ：先行燃料集合体４（１）における冷却材密度係数
ΔＴ 、先行燃料集合体４（ｉ）以外の燃〕
粗菓合体の冷却材温度上昇
Ｗ ：先行燃料集合体４（ｉ）以外の燃粗菓合体の冷却
材密度係数
そして、前記（１）式より先行燃料集合体４（ｊ）の出
力−流量比が他の燃料集合体２より大きいから、
ΔＴ 〉ΔＴ、にｎ Ｔ ）−（５）となり、さら
に、先行燃料集合体４の冷却材密度係数に対する条件を
求めた前記（３）式から、炉心１全体に挿入される冷却
材反応度Δρ が負値となる。ΔT ・Coolant temperature rise in the preceding fuel assembly 4(i)) W: Coolant density coefficient ΔT in the preceding fuel assembly 4(1), combustion other than the preceding fuel assembly 4(i)] Cooling of the coarse aggregate Material temperature rise W: coolant density coefficient of the fuel assembly other than the preceding fuel assembly 4(i), and from the above equation (1), the output-flow rate ratio of the preceding fuel assembly 4(j) is higher than that of the other fuel assembly. Since ΔT > ΔT, n T ) - (5), and furthermore, from equation (3) above, which determined the condition for the coolant density coefficient of the preceding fuel assembly 4, it is determined that the coolant is inserted into the entire core 1. The coolant reactivity Δρ becomes a negative value.
つまり、万一、原子炉スクラム信号か発生したにも拘ら
ず、制御棒３が挿入されない事態になっても、先行燃料
集合体４には炉心平均より先行した温度上昇が生じ、そ
の結果として炉心全体に負の反応度が挿入され、原子炉
は炉停止状態に移行し、安全に炉停止する。In other words, even if the control rods 3 are not inserted even though a reactor scram signal is generated, the temperature of the preceding fuel assembly 4 will rise in advance of the core average, and as a result, the core A negative reactivity is inserted throughout, and the reactor transitions to a reactor shutdown state, safely shutting down the reactor.
したがって、炉心１全体の冷却材密度係数の総和が正値
である場合でも、先行燃料集合体４により負の冷却材反
応度が挿入されるので、炉心燃料を損傷させずに炉停止
される。Therefore, even if the sum of the coolant density coefficients of the entire core 1 is a positive value, negative coolant reactivity is inserted by the preceding fuel assembly 4, so the reactor is shut down without damaging the core fuel.
次に、前記冷却材温度上昇かさらに顕著になりた場合の
作用について説明する。Next, an explanation will be given of the effect when the coolant temperature rise becomes more significant.
万一、前記質の反応度効果が不十分て、冷却材の温度上
昇が著しい場合は先行燃料集合体４ては冷却材の沸騰か
発生する。In the unlikely event that the reactivity effect of the above-mentioned quality is insufficient and the temperature of the coolant rises significantly, boiling of the coolant will occur in the preceding fuel assembly 4.
第５図はこのような沸騰自体における燃料集合体の冷却
材温度と８カー流量比との関係を示しており、図示のよ
うに先行燃料集合体４の冷却材最高温度（Ｅ）は沸点Ｔ
Ｂに到達しているか、他の燃料集合体２ではまだ冷却材
が単相（Ｆ）に止まっている。FIG. 5 shows the relationship between the coolant temperature of the fuel assembly and the 8 car flow rate ratio during such boiling itself, and as shown in the figure, the maximum coolant temperature (E) of the preceding fuel assembly 4 is equal to the boiling point T.
B has been reached, or the coolant remains in a single phase (F) in other fuel assemblies 2.
このために、係る状況においては先行燃料集合体４では
冷却材ボイド反応度Ｋ が挿入され、炉■
心金体では次の（６）式で示される冷却材反応度が挿入
される。For this reason, in such a situation, a coolant void reactivity K is inserted in the preceding fuel assembly 4, and a coolant reactivity expressed by the following equation (6) is inserted in the core metal body.
Δρ。Δρ.
ここては、炉心１全体に挿入される冷却材反応度は殆ど
先行燃料集合体４の負ホイドであるため、炉ａ力は急速
に減衰し、炉心燃料の損傷に至ることなく事故は安全に
終息する。Here, since the reactivity of the coolant inserted into the entire core 1 is mostly the negative hoid of the preceding fuel assembly 4, the reactor a-force is rapidly attenuated, and the accident can be safely avoided without causing damage to the core fuel. End.
さらに、万一、ボイド化した先行燃料集合体４て燃料破
損か生じた場合について説明する。Furthermore, a case will be described in which fuel damage occurs in the voided preceding fuel assembly 4.
先行燃料集合体４において冷却材のボイド化が進展した
段階で、万一、炉停止が不十分であると、この先行燃料
集合体４では燃料ピン８の破砕現象か発生し、微粒化し
た燃料は燃料ペレット１０内のＦＰガスを駆動圧として
上下方向（軸方向）に分散する。If the reactor is not shut down sufficiently at the stage where the voiding of the coolant has progressed in the preceding fuel assembly 4, the fuel pins 8 may be crushed in this preceding fuel assembly 4, resulting in atomized fuel. is dispersed in the vertical direction (axial direction) using the FP gas in the fuel pellet 10 as a driving pressure.
このような軸方向の先行燃料集合体４内部での燃料分散
現象は各種の炉内燃料破損試験で確認されている。Such a phenomenon of fuel dispersion inside the preceding fuel assembly 4 in the axial direction has been confirmed in various in-core fuel failure tests.
このような先行燃料集合体４の破損は第６図に示すよう
に、燃料ピン束８ａの軸方向中間部近傍Ｇで破損した破
砕燃料Ｈは上下方向に分散し移動する。As shown in FIG. 6, when the preceding fuel assembly 4 is damaged, the crushed fuel H that is damaged near the axially intermediate portion G of the fuel pin bundle 8a is dispersed and moved in the vertical direction.
そして、下方向に移動した燃料は燃料ピン束８ａ下部の
単相冷却材か存在している領域Ｉで固化Ｊするか、上方
向に移動した破砕燃料Ｈは燃料ピン束８ａの上方か中空
部１２であるために開口上端の出口９ｂから外部に流出
する。Then, the fuel that has moved downward is solidified in the area I where the single-phase coolant is present at the bottom of the fuel pin bundle 8a, or the crushed fuel H that has moved upward is either above the fuel pin bundle 8a or in the hollow area. 12, it flows out from the outlet 9b at the upper end of the opening.
この流出燃料Ｍは燃料ピン束８ａ部では大きな抵抗を受
けて再固化し易いか、燃料ピン束８ａの直上か中空部１
２てあり、水力等価直径が大きいため、容易に燃料か流
出する。This spilled fuel M is easily re-solidified due to large resistance in the fuel pin bundle 8a, or is it directly above the fuel pin bundle 8a or in the hollow part 1?
2, and the hydraulic equivalent diameter is large, so fuel easily flows out.
この結果、炉中心に近い軸方向の燃料反応度価値の大き
な領域から燃料が排除されることとなり、大きな負反応
度（燃料反応度）か挿入される。As a result, fuel is removed from the region of large fuel reactivity value in the axial direction near the center of the reactor, and a large negative reactivity (fuel reactivity) is inserted.
したがって、炉出力は著しく抑制され、炉停止に移行す
る結果、事故は安全に終息する。そして、このような燃
料破損は先行燃料集合体４のみに限定されて炉心全体に
亘る燃料焼損を防止することかできる。Therefore, the reactor output is significantly suppressed and the reactor is shut down, resulting in a safe end to the accident. Such fuel damage is limited to only the preceding fuel assembly 4, and fuel burnout throughout the core can be prevented.
し発明の効果〕
以上説明したように本発明は、炉心の冷却材密度係数な
いしボイド係数が負値をなす領域に、出力−流量比が他
の燃料集合体のものよりも大きい先行燃料集合体を配置
したので、炉停止失敗という極低頻度事象が発生した場
合には、先行燃料集合体により負の冷却材反応度を先行
的に炉心に挿入して炉停止状態にするので、炉心燃料の
損傷に至ることなく未然にかつ安全に事故を終息させて
炉停止することができる。[Effects of the Invention] As explained above, the present invention provides a preceding fuel assembly whose output-flow ratio is larger than that of other fuel assemblies in a region where the coolant density coefficient or void coefficient of the core has a negative value. With this arrangement, in the event that an extremely low-frequency event such as reactor shutdown failure occurs, negative coolant reactivity is inserted into the reactor core in advance using the advance fuel assembly to bring the reactor to a shutdown state, thereby reducing the amount of core fuel. It is possible to terminate the accident and shut down the reactor safely and without causing any damage.
また、万一、冷却材か沸騰した場合でも、燃料破損を先
行燃料集合体に止め、かつ負のボイド反応度を挿入する
ことにより事故を終息させることかできる。Furthermore, even if the coolant boils, the accident can be brought to an end by preventing fuel damage to the preceding fuel assembly and inserting negative void reactivity.
さらに、万一、燃料破損に至る場合でも、その燃料破損
を先行燃料集合体内に限定すると共に、速かに破砕燃料
を集合体外に流出せしめ、さらなる負の燃料反応度挿入
により炉停止させ、事故を完全に終息させることかでき
る。Furthermore, in the unlikely event that fuel damage occurs, the fuel damage will be limited to the preceding fuel assembly, the shredded fuel will quickly flow out of the assembly, and further negative fuel reactivity will be inserted to shut down the reactor and cause an accident. It is possible to completely end it.
つまり、原子炉自体の自然の原理により炉停止すること
かでき、原子炉の究極的な安全性を確保することができ
る。In other words, the reactor can be shut down using the natural principles of the reactor itself, and the ultimate safety of the reactor can be ensured.
第１図は本発明に係る高速炉炉心の一実施例の概略平面
図、第２図は第１図で示す先行燃料集合体の縦断面図、
第３図は第１図で示す実施例における燃料集合体の出力
−流量比スペクトルを示すグラフ、第４図は第１図で示
す実施例における冷却材密度係数の炉心径方向分布図、
第５図は第１図で示す実施例における炉停止失敗事象発
生時の集合体冷却材温度と出力−流量比との関係を示す
グラフ、第６図は第１図で示す先行燃料集合体の燃料破
損時の挙動を示す模式図である。
１・・・炉心、２・・・燃料集合体、３・・・制御棒、
４・・・先行燃料集合体、５・・・隣接燃料集合体、６
・・・中性子遮蔽体。
出願人代理人 波 多 野 久 −ａ
■−５
■−３
■−ぎ
＄１ 回
渠
図
梁
図
１θ
集合伴出カーフ飛量比（相対儀）
第
固
ｌθ
２．０
Ｓ合体出力−流量比（相対イ創
羊
図
茶
図FIG. 1 is a schematic plan view of an embodiment of a fast reactor core according to the present invention, FIG. 2 is a longitudinal sectional view of the preceding fuel assembly shown in FIG. 1,
3 is a graph showing the power-flow rate ratio spectrum of the fuel assembly in the embodiment shown in FIG. 1, FIG. 4 is a core radial distribution diagram of the coolant density coefficient in the embodiment shown in FIG. 1,
FIG. 5 is a graph showing the relationship between the assembly coolant temperature and the output-flow ratio when a reactor shutdown failure event occurs in the example shown in FIG. 1, and FIG. FIG. 3 is a schematic diagram showing behavior when fuel is damaged. 1... Core, 2... Fuel assembly, 3... Control rod,
4...Advanced fuel assembly, 5...Adjacent fuel assembly, 6
...Neutron shield. Applicant's agent Hisashi Hatano -a ■-5 ■-3 ■-gi $1 Drain diagram beam diagram 1θ Collective lead out calf flight ratio (relative) 1st solid lθ 2.0 S combined output-flow rate ratio (Relative Yi Chuang Sheep Chart
Claims (1)
の燃料集合体を装荷して、冷却材密度係数ないしボイド
係数が負値をなす領域を有する高速炉炉心において、前
記冷却材密度係数ないしボイド係数が負値をなす領域に
ある前記燃料集合体の少なくとも一部を、その出力／流
量比が他の前記燃料集合体のものよりも大きい先行燃料
集合体に構成したことを特徴とする高速炉炉心。In a fast reactor core loaded with a plurality of fuel assemblies containing a plurality of fuel elements through which coolant can flow freely, and having a region where the coolant density coefficient or void coefficient takes a negative value, the coolant density coefficient At least some of the fuel assemblies in a region where the void coefficient takes a negative value are configured as preceding fuel assemblies whose output/flow ratio is larger than that of the other fuel assemblies. Fast reactor core.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2194789A JPH0481695A (en) | 1990-07-25 | 1990-07-25 | Core of fast reactor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2194789A JPH0481695A (en) | 1990-07-25 | 1990-07-25 | Core of fast reactor |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH0481695A true JPH0481695A (en) | 1992-03-16 |
Family
ID=16330290
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2194789A Pending JPH0481695A (en) | 1990-07-25 | 1990-07-25 | Core of fast reactor |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0481695A (en) |
-
1990
- 1990-07-25 JP JP2194789A patent/JPH0481695A/en active Pending
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