JP4863414B2 - Thermal fluid phenomenon simulation method and simulation test apparatus - Google Patents

Thermal fluid phenomenon simulation method and simulation test apparatus Download PDF

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JP4863414B2
JP4863414B2 JP2007105374A JP2007105374A JP4863414B2 JP 4863414 B2 JP4863414 B2 JP 4863414B2 JP 2007105374 A JP2007105374 A JP 2007105374A JP 2007105374 A JP2007105374 A JP 2007105374A JP 4863414 B2 JP4863414 B2 JP 4863414B2
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森昌司
奥山邦人
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Description

本発明は、熱流動現象の模擬方法及び模擬試験装置に関するものであり、より詳細には、沸騰水型原子炉内の高温・高圧環境に存在する沸騰二相流の熱流動現象を常温・低圧の環境で再現する熱流動現象の模擬方法及び模擬試験装置に関するものである。   The present invention relates to a thermal fluid phenomenon simulation method and a simulation test apparatus. More specifically, the present invention relates to a thermal fluid phenomenon of a boiling two-phase flow existing in a high-temperature and high-pressure environment in a boiling water reactor. The present invention relates to a simulation method and simulation test apparatus for a heat flow phenomenon reproduced in an environment of the above.

沸騰水型原子炉（ＢＷＲ）の原子炉圧力容器内に配置される燃料集合体においては、燃料棒は、例えば、数mm程度の間隔で正方格子状に稠密に配置され、冷却材としての水が単相流の状態で燃料集合体の下部から流入し、発熱する燃料棒の間隙を流動し、燃料棒の発熱によって沸騰しながら燃料棒の間の間隙を上昇する。蒸気及び水の沸騰二相流が燃料集合体の内部に発生するので、炉心熱設計を行う場合、この沸騰二相流の挙動を詳細に把握する必要がある。   In a fuel assembly arranged in a reactor pressure vessel of a boiling water reactor (BWR), fuel rods are densely arranged in a square lattice at intervals of about several millimeters, for example, and water as a coolant. Flows in from the lower part of the fuel assembly in a single-phase flow state, flows through the gap between the fuel rods that generate heat, and rises through the gap between the fuel rods while boiling due to the heat generated by the fuel rods. Since a boiling two-phase flow of steam and water is generated inside the fuel assembly, it is necessary to grasp the behavior of the boiling two-phase flow in detail when designing the core thermal design.

燃料棒の限界出力（限界熱流束）付近では、高速の蒸気流が燃料棒廻りに生成するので、極めて薄い液膜が環状流として燃料棒の外周面を覆い、熱伝達率が非常に高い状態が燃料棒の伝熱表面に生じる。更に出力が上昇すると、燃料棒表面の液膜が蒸発して燃料棒表面が乾く液膜ドライアウト現象が発生する。このようなドライアウトが一旦発生すると、熱伝達率が急激に悪化するので、燃料棒の壁温が急上昇し、場合によっては発熱管の焼損（バーンアウト）現象が発生し得る。このため、このような限界条件における燃料棒上の液膜挙動を正確に把握することは、原子炉の熱設計を行う上で極めて重要である。   Near the limit output (limit heat flux) of the fuel rod, a high-speed steam flow is generated around the fuel rod, so an extremely thin liquid film covers the outer surface of the fuel rod as an annular flow, and the heat transfer coefficient is very high. On the heat transfer surface of the fuel rod. When the output further increases, the liquid film on the fuel rod surface evaporates and the fuel rod surface dries out, resulting in a liquid film dryout phenomenon. Once such dryout occurs, the heat transfer rate deteriorates rapidly, so the wall temperature of the fuel rod rises rapidly, and in some cases, a heat-out tube burnout phenomenon may occur. For this reason, accurately grasping the behavior of the liquid film on the fuel rod under such limit conditions is extremely important for the thermal design of the nuclear reactor.

従来、沸騰水型原子炉の開発・設計では、開発から実証に至る過程において、試験・実験的アプローチが重視されてきた。現状では、原子炉燃料の開発・設計は、実機条件（圧力7MPa、温度285 ℃）の実証試験（電気加熱）を行い、設計変更又は条件変更を繰り返して最適化を図るという手法が採用されている。このような開発・設計手法では、高温高圧試験を繰り返し実施しなければならないことから、莫大なコスト及び時間が必要とされる。例えば、原子炉燃料の設計を最適化するには、数週間を要する高額な実証試験を数十回も繰り返し実施して改良を図る必要が生じる。このような試験・実験的アプローチは、コスト及び時間的な不利を生じさせるのみならず、燃料の大型化や、格子稠密化等の近年の傾向と関連して、試験・実験機器の容量的な問題を生じさせており、試験・実験的アプローチを採用すること自体、困難になりつつある。このため、試験・実験に依存した開発・設計から解析中心の開発・設計への移行が望まれるとともに、簡易且つ効率的に試験・実験を行うことができる試験・実験方法及び試験・実験機器の開発が要望される。   Conventionally, in the development and design of boiling water reactors, testing and experimental approaches have been emphasized in the process from development to demonstration. At present, the development and design of nuclear reactor fuel is based on the actual equipment conditions (pressure 7MPa, temperature 285 ° C) through verification tests (electric heating), and the design changes or conditions are repeatedly optimized for optimization. Yes. In such a development / design method, a high temperature and high pressure test must be repeatedly performed, and thus enormous costs and time are required. For example, in order to optimize the design of a nuclear reactor fuel, it is necessary to repeatedly carry out an expensive demonstration test that takes several weeks and repeat it several tens of times. Such a test / experimental approach not only causes cost and time disadvantages, but also relates to recent trends such as fuel upsizing and grid densification, and the capacity of test / experimental equipment. It is causing problems, and adopting a test and experimental approach itself is becoming difficult. For this reason, it is desirable to shift from development / design depending on testing / experiment to analysis-centric development / design, as well as testing / experimental methods and testing / experimental equipment that can perform testing / experiments easily and efficiently. Development is required.

熱流動現象の試験・実験を簡易且つ効率的に実施することを可能にする方法として、６フッ化硫黄ガスを液体アルコールに噴霧して気液二相流を形成し、高温・高圧環境の気液二相流を低温・低圧環境において模擬する模擬試験方法が特開２００２−１８９０９６号公報に開示されている。しかしながら、この模擬試験方法は、加圧水型原子炉（ＰＷＲ型原子炉）の蒸気発生器における気液二相流の流動現象を６フッ化硫黄ガス及び液体アルコールの気液二相流によって模擬し、液滴分離装置の液滴分離性能を評価することを意図したものであるにすぎない。
特開２００２−１８９０９６号公報 As a method that enables simple and efficient testing and experiments of thermal fluid phenomena, sulfur hexafluoride gas is sprayed onto liquid alcohol to form a gas-liquid two-phase flow. Japanese Laid-Open Patent Publication No. 2002-189096 discloses a simulation test method for simulating a liquid two-phase flow in a low temperature / low pressure environment. However, this simulation test method simulates the flow phenomenon of a gas-liquid two-phase flow in a steam generator of a pressurized water reactor (PWR reactor) by a gas-liquid two-phase flow of sulfur hexafluoride gas and liquid alcohol, It is only intended to evaluate the droplet separation performance of the droplet separator.
JP 2002-189096 A

沸騰水型原子炉（ＢＷＲ型原子炉）の液膜ドライアウト現象は、気液二相流自体の挙動や物性に関連するのみならず、気液二相流の流動によって伝熱表面に生じる液膜の挙動と密接に関連する。即ち、沸騰水型原子炉の燃料集合体内を上昇する沸騰二相流は、前述の如く、燃料棒の表面(伝熱表面)に薄い液膜を形成するが、この液膜は、燃料棒の伝熱表面において非常に激しく変動し、複雑な液膜挙動を示すと考えられるので、液膜ドライアウトの発生条件等を正確に把握するには、このような液膜の挙動を模擬する必要がある。   The liquid film dry-out phenomenon in a boiling water reactor (BWR reactor) is not only related to the behavior and physical properties of the gas-liquid two-phase flow itself, but also the liquid generated on the heat transfer surface due to the flow of the gas-liquid two-phase flow. It is closely related to the behavior of the membrane. That is, the boiling two-phase flow rising in the fuel assembly of the boiling water reactor forms a thin liquid film on the surface (heat transfer surface) of the fuel rod as described above. Since it is considered that the heat transfer surface fluctuates very severely and exhibits complex liquid film behavior, it is necessary to simulate such liquid film behavior in order to accurately grasp the conditions of liquid film dryout. is there.

他方、解析を中心として原子炉の開発・設計手法として、サブチャンネル解析コード(NASCA)が知られており、この解析手法を改良して原子炉の汎用的解析手法を確立するための研究が、多くの研究者によって実施されている。しかし、沸騰水型原子炉の炉内には、燃料棒の除熱性能に大きく影響を与える複数の因子が存在し、これらの因子は、解析手法の確立を困難にしている。例えば、沸騰水型原子炉の炉内には、燃料棒の振動を抑制し且つ相互接触を防止するためのスペーサが燃料集合体の適所に配置されており、燃料棒表面の液膜は、スペーサの近傍において複雑に膜厚を変化させる。このため、スペーサの形状及び位置は、燃料棒の限界出力を設定する上で極めて重要な因子であるが、スペーサが燃料棒表面の液膜挙動に与える影響は、極めて予測し難く、燃料棒近傍の熱流動現象に対するスペーサの影響を定量的に評価する手法は、依然として確立されていない。   On the other hand, the subchannel analysis code (NASCA) is known as a nuclear reactor development and design method centering on analysis, and research to improve this analysis method and establish a general-purpose analysis method for nuclear reactors, It has been implemented by many researchers. However, there are a number of factors that greatly affect the heat removal performance of fuel rods in boiling water reactors, and these factors make it difficult to establish analytical methods. For example, in a furnace of a boiling water reactor, a spacer for suppressing vibration of the fuel rod and preventing mutual contact is disposed at an appropriate position of the fuel assembly. The film thickness is complicatedly changed in the vicinity. For this reason, the shape and position of the spacer are extremely important factors in setting the limit output of the fuel rod, but the effect of the spacer on the liquid film behavior on the surface of the fuel rod is extremely difficult to predict, and the vicinity of the fuel rod A method for quantitatively evaluating the influence of the spacer on the heat flow phenomenon of the material has not been established yet.

本発明は、このような事情に鑑みてなされたものであり、その目的とするところは、高温・高圧の沸騰水型原子炉内に発生する沸騰二相流の熱流動現象を常温・低圧の環境で再現し、沸騰二相流が燃料棒の伝熱表面に形成する液膜の挙動を常温・低圧の環境で模擬するとともに、液膜挙動の測定を可能にし、これにより、燃料棒の除熱性能に大きく影響を与える因子の定量的評価を可能にする熱流動現象の模擬方法及び模擬試験装置を提供することにある。   The present invention has been made in view of such circumstances, and the object of the present invention is to analyze the heat flow phenomenon of boiling two-phase flow generated in a high-temperature / high-pressure boiling water reactor at room temperature / low pressure. It reproduces in the environment, and simulates the behavior of the liquid film formed on the heat transfer surface of the fuel rod by boiling two-phase flow in a normal temperature / low pressure environment, and enables measurement of the liquid film behavior. It is an object of the present invention to provide a simulation method and simulation test apparatus for a thermal fluid phenomenon that enables quantitative evaluation of factors that greatly affect thermal performance.

本発明は、上記目的を達成すべく、沸騰水型原子炉内の高温・高圧環境に存在する沸騰二相流の熱流動現象を再現する熱流動現象の模擬方法において、
前記沸騰二相流の密度、表面張力及び粘度の物性値と実質的に同一又は同等の密度、表面張力及び粘度の物性値を常温・低圧の環境で示す二相流体の流れを液体及び気体の混合流体によって形成し、
前記二相流体を所定断面且つ常温・低圧の直線流路に通して、該流路の流路壁面に液膜を形成し、高温・高圧の環境で前記沸騰二相流が前記沸騰水型原子炉の燃料棒の伝熱表面に形成する液膜を常温・低圧の環境で流路壁面に再現して該液膜の挙動を模擬し、
前記液膜の膜厚及び／又は液膜流量を測定することを特徴とする熱流動現象の模擬方法を提供する。 In order to achieve the above object, the present invention provides a method for simulating a thermal fluid phenomenon that reproduces the thermal fluid phenomenon of a boiling two-phase flow existing in a high temperature and high pressure environment in a boiling water reactor.
The flow of a two-phase fluid showing the physical properties of density, surface tension and viscosity substantially the same or equivalent to the physical properties of density, surface tension and viscosity of the boiling two-phase flow in a normal temperature / low pressure environment. Formed by a mixed fluid,
The two-phase fluid is passed through a straight channel having a predetermined cross section and a normal temperature / low pressure, and a liquid film is formed on the channel wall surface of the channel, and the boiling two-phase flow is generated in the boiling water atom in a high temperature / high pressure environment. The liquid film formed on the heat transfer surface of the fuel rod of the furnace is reproduced on the wall surface of the flow path in a normal temperature / low pressure environment to simulate the behavior of the liquid film,
Provided is a method for simulating a thermal fluid phenomenon, wherein the film thickness and / or the liquid film flow rate of the liquid film is measured.

本発明の上記構成によれば、沸騰水型原子炉内の沸騰二相流の流れを模擬する二相流体の流れが、直線流路内に形成される。燃料棒の伝熱表面の液膜挙動が常温・低圧の環境で流路壁面に模擬され、液膜の膜厚及び／又は液膜流量が常温・低圧の環境で測定される。このような模擬方法によれば、例えば、スペーサを模擬する障害物を流路内に配置した状態で液膜挙動を模擬することができ、これにより、スペーサが液膜挙動に与える影響を分析し、サブチャンネル解析コード(NASCA)に適用可能なスペーサ増倍係数等を設定することが可能となる。   According to the above configuration of the present invention, the flow of the two-phase fluid that simulates the flow of the boiling two-phase flow in the boiling water reactor is formed in the straight flow path. The behavior of the liquid film on the heat transfer surface of the fuel rod is simulated on the channel wall surface in a normal temperature / low pressure environment, and the liquid film thickness and / or liquid film flow rate is measured in a normal temperature / low pressure environment. According to such a simulation method, for example, the liquid film behavior can be simulated in a state where an obstacle that simulates the spacer is arranged in the flow path, thereby analyzing the influence of the spacer on the liquid film behavior. It is possible to set a spacer multiplication factor applicable to the subchannel analysis code (NASCA).

なお、本明細書において、「常温」は、概ね室温又は大気温度に相当する温度範囲（概ね０℃から５０℃の範囲）の温度を意味し、「低圧」は、通常の実験機器によって形成可能な範囲（概ね０．１〜１MPaの範囲）の圧力を意味する。   In the present specification, “normal temperature” means a temperature in a temperature range (approximately 0 ° C. to 50 ° C.) corresponding to room temperature or atmospheric temperature, and “low pressure” can be formed by ordinary laboratory equipment. Pressure within a wide range (approximately 0.1 to 1 MPa).

好ましくは、上記液体は、エタノールであり、上記気体は、HFC134a ガスである。更に好ましくは、流路方向に間隔を隔てた複数の計測点における液膜の膜厚が、電気抵抗法（例えば、定電流法）又は光学的な測定法によって計測される。   Preferably, the liquid is ethanol and the gas is HFC134a gas. More preferably, the film thickness of the liquid film at a plurality of measurement points spaced apart in the flow path direction is measured by an electric resistance method (for example, a constant current method) or an optical measurement method.

本発明は又、上記模擬方法によって限界出力を最適化した燃料集合体を有する沸騰水型原子炉を提供する。   The present invention also provides a boiling water nuclear reactor having a fuel assembly that has a critical power optimized by the simulation method.

本発明は更に、沸騰水型原子炉内の高温・高圧環境に存在する沸騰二相流の熱流動現象を再現する熱流動現象の模擬試験装置において、
前記沸騰二相流の密度、表面張力及び粘度の物性値と実質的に同一又は同等の密度、表面張力及び粘度の物性値を常温・低圧の環境で示す二相流体が供給される常温・低圧の直線流路と、
前記二相流体を形成する液体及び気体の混合流体を前記直線流路に供給する流体供給手段と、
前記混合流体によって前記直線流路の流路壁面に形成された液膜の膜厚及び／又は液膜流量を測定する液膜計測手段とを備え、
前記沸騰水型原子炉の燃料棒の伝熱表面に形成される液膜を常温・低圧の環境で前記流路壁面に再現して前記液膜の挙動を模擬するとともに、前記液膜の膜厚及び／又は液膜流量を測定するようにしたことを特徴とする熱流動現象の模擬試験装置を提供する。 The present invention further relates to a thermal fluid phenomenon simulation test apparatus that reproduces the thermal fluid phenomenon of a boiling two-phase flow existing in a high temperature and high pressure environment in a boiling water reactor.
Normal temperature / low pressure at which a two-phase fluid is supplied that exhibits physical properties of density, surface tension and viscosity substantially the same or equivalent to the physical properties of density, surface tension and viscosity of the boiling two-phase flow. A straight channel of
Fluid supply means for supplying a fluid mixture of liquid and gas forming the two-phase fluid to the linear flow path;
A liquid film measuring means for measuring the film thickness and / or the liquid film flow rate of the liquid film formed on the flow channel wall surface of the linear flow channel by the mixed fluid,
The liquid film formed on the heat transfer surface of the fuel rod of the boiling water reactor is reproduced on the wall surface of the flow path in a room temperature / low pressure environment to simulate the behavior of the liquid film, and the film thickness of the liquid film And / or a thermal fluid phenomenon simulation test apparatus characterized by measuring a liquid film flow rate.

例えば、模擬試験装置は、流路方向に所定間隔を隔てた複数の計測点において液膜の膜厚を電気抵抗法又は光学的測定法によって計測する膜厚計測手段や、液膜流量計測手段を備える。   For example, the simulation test apparatus includes a film thickness measuring means for measuring the film thickness of the liquid film by an electric resistance method or an optical measurement method at a plurality of measurement points separated by a predetermined interval in the flow path direction, and a liquid film flow rate measuring means. Prepare.

本発明の模擬方法及び模擬試験装置によれば、高温・高圧の沸騰水型原子炉内に発生する沸騰二相流の熱流動現象を常温・低圧の環境で再現し、沸騰二相流が燃料棒の伝熱表面に形成する液膜の挙動を常温・低圧の環境で模擬するとともに、液膜の挙動を測定することができる。このような模擬方法及び模擬試験装置においては、例えば、スペーサを模擬する障害物を流路に配置することにより、スペーサの影響等を定量的に評価することができ、従って、本発明によれば、燃料棒の除熱性能に大きく影響を与える因子を定量的に評価することが可能となる。これは、サブチャンネル解析コード(NASCA)による解析法の精度向上に大きく寄与するであろう。   According to the simulation method and the simulation test apparatus of the present invention, the heat flow phenomenon of a boiling two-phase flow generated in a high-temperature / high-pressure boiling water reactor is reproduced in a room temperature / low pressure environment, and the boiling two-phase flow is a fuel. The behavior of the liquid film formed on the heat transfer surface of the rod can be simulated in a normal temperature / low pressure environment, and the behavior of the liquid film can be measured. In such a simulation method and a simulation test apparatus, for example, the influence of the spacer can be quantitatively evaluated by placing an obstacle that simulates the spacer in the flow path. In addition, it is possible to quantitatively evaluate the factors that greatly affect the heat removal performance of the fuel rods. This will greatly contribute to improving the accuracy of the analysis method using the subchannel analysis code (NASCA).

図１は、燃料集合体の構成を部分的に示す正面図及び横断面図である。   FIG. 1 is a front view and a cross-sectional view partially showing a configuration of a fuel assembly.

沸騰水型原子炉の炉心を構成する複数の燃料集合体１が、図１に部分的に示されている。燃料集合体１は、所定間隔を隔てて垂直な燃料棒２を稠密に配置した構成を有する。燃料棒間ギャップを一定に保持するための複数のスペーサ３が、燃料棒２の軸芯方向に所定間隔を隔てて配置される。冷却材としての水が単相流の状態で燃料集合体１の下部から流入し、矢印で示すように上昇する。水は、燃料棒２の発熱によって沸騰し、蒸気及び水の沸騰二相流として燃料棒２の間の間隙４を上昇する。図１（Ｂ）には、円形断面のスペーサ３が例示され、図１（Ｃ）には、六角形断面のスペーサ３が例示されている。   A plurality of fuel assemblies 1 constituting the core of a boiling water reactor are partially shown in FIG. The fuel assembly 1 has a configuration in which vertical fuel rods 2 are densely arranged at a predetermined interval. A plurality of spacers 3 for maintaining a constant gap between the fuel rods is arranged in the axial direction of the fuel rod 2 at a predetermined interval. Water as a coolant flows in from a lower portion of the fuel assembly 1 in a single-phase flow state and rises as indicated by an arrow. Water boils due to the heat generated by the fuel rods 2 and rises in the gap 4 between the fuel rods 2 as a boiling two-phase flow of steam and water. FIG. 1B illustrates a spacer 3 having a circular cross section, and FIG. 1C illustrates a spacer 3 having a hexagonal cross section.

図２は、燃料棒２の管壁５を部分的に拡大して示す部分拡大断面図である。   FIG. 2 is a partially enlarged cross-sectional view showing the tube wall 5 of the fuel rod 2 partially enlarged.

上昇する沸騰二相流は、環状流として燃料棒２の外周面を覆い、薄い液膜１０が燃料棒２の表面（伝熱表面）に形成される。液膜１０は、燃料棒２の伝熱表面の熱伝達率を向上させる。大小様々な液塊（図示せず）が燃料棒２の表層近傍を頻繁に通過し、液膜１０は、非常に激しく変動し、じょう乱波１１として示す如く、複雑且つ非定常な液膜挙動を生じさせる。沸騰二相流は、スペーサ３の近傍では、更に複雑な流動様相を示す。従って、燃料棒２の伝熱表面における液膜挙動の態様及び性質は、現状では、判明していない。   The rising boiling two-phase flow covers the outer peripheral surface of the fuel rod 2 as an annular flow, and a thin liquid film 10 is formed on the surface (heat transfer surface) of the fuel rod 2. The liquid film 10 improves the heat transfer coefficient of the heat transfer surface of the fuel rod 2. Various large and small liquid masses (not shown) frequently pass in the vicinity of the surface layer of the fuel rod 2, and the liquid film 10 fluctuates very violently. Give rise to The boiling two-phase flow shows a more complicated flow pattern in the vicinity of the spacer 3. Therefore, the mode and nature of the liquid film behavior on the heat transfer surface of the fuel rod 2 are not known at present.

更に出力が上昇すると、燃料棒表面の液膜が蒸発して燃料棒表面が乾く液膜ドライアウト現象（符号１２で示す）が発生する。このようなドライアウトが一旦発生すると、熱伝達率が急激に悪化するので、燃料棒２は、その壁温が急上昇し、場合によっては管壁５の焼損（バーンアウト）現象が発生し得る。このため、このような限界条件における燃料棒上の液膜挙動を正確に把握することは、原子炉の熱設計を行う上で極めて重要である。   When the output further increases, the liquid film on the fuel rod surface evaporates and the fuel rod surface dries out, and a liquid film dry-out phenomenon (indicated by reference numeral 12) occurs. Once such a dryout occurs, the heat transfer rate deteriorates rapidly, so that the wall temperature of the fuel rod 2 rises rapidly, and in some cases, a burnout phenomenon of the tube wall 5 may occur. For this reason, accurately grasping the behavior of the liquid film on the fuel rod under such limit conditions is extremely important for the thermal design of the nuclear reactor.

図３は、スペーサ３の近傍に生じる液膜挙動を例示する部分拡大断面図である。   FIG. 3 is a partially enlarged cross-sectional view illustrating the liquid film behavior that occurs in the vicinity of the spacer 3.

前述の如く、スペーサ３の形状・寸法及び位置が液膜１０の挙動に与える影響は、極めて複雑である。例えば、液膜１０の膜厚は、図３に示すようにスペーサ３の近傍で局部的に大きく低減し又は増大する傾向があると考えられ、スペーサ３の近傍では、液膜ドライアウト現象（符号１２）が発生することが懸念される。燃料集合体１の流路を模式的に各燃料棒２毎の小流路（サブチャンネル）に分割して燃料集合体１内の熱流動現象を解析するサブチャンネル解析が、燃料集合体１の限界出力を求めるために近年使用されているが、スペーサ３の存在は、液膜ドライアウト現象と密接に関連することから、スペーサ３の影響をサブチャンネル解析に反映することが望まれる。   As described above, the influence of the shape, size, and position of the spacer 3 on the behavior of the liquid film 10 is extremely complicated. For example, it is considered that the film thickness of the liquid film 10 tends to greatly decrease or increase locally near the spacer 3 as shown in FIG. 12) is a concern. Subchannel analysis in which the flow path of the fuel assembly 1 is schematically divided into small flow paths (subchannels) for each fuel rod 2 to analyze the thermal flow phenomenon in the fuel assembly 1 is Although it has been used in recent years to determine the limit output, the presence of the spacer 3 is closely related to the liquid film dryout phenomenon, so it is desirable to reflect the influence of the spacer 3 on the subchannel analysis.

図４には、燃料棒２を模擬した発熱管上に生じる液膜の膜厚変動特性が示されている。   FIG. 4 shows the film thickness fluctuation characteristics of the liquid film generated on the heat generating tube simulating the fuel rod 2.

図４に示す変動特性は、本発明者が大気圧の実験環境において従来の実験機器を用いて実施した模擬実験の実験結果である。この模擬実験では、水蒸気の見掛け流速（jG) を16.6m/s に設定し、水の見掛け流速（jL) を0.41m/s に設定している。 The fluctuation characteristics shown in FIG. 4 are experimental results of a simulation experiment conducted by the inventor using a conventional experimental device in an experimental environment at atmospheric pressure. In this simulation experiment, the apparent flow velocity (j G ) of water vapor is set to 16.6 m / s, and the apparent flow velocity (j L ) of water is set to 0.41 m / s.

図４に示す変動特性から理解し得るように、発熱管上に形成される液膜は、非常に激しく変動しており、大小様々な液塊が発熱管近傍を頻繁に通過する複雑な液膜挙動を示す。このような実験による観察や計測等は、或る程度までは高温・高圧の条件で実施し得るかもしれない。   As can be understood from the fluctuation characteristics shown in FIG. 4, the liquid film formed on the heat generation tube fluctuates extremely violently, and a complicated liquid film in which large and small liquid masses frequently pass near the heat generation tube. Shows behavior. Such observation and measurement by experiments may be carried out under high temperature and high pressure conditions to a certain extent.

しかし、沸騰水型原子炉（実機）の一般的な設計条件では、燃料集合体１の内部環境は、圧力7MPa、温度285 ℃に達する。従って、沸騰水型原子炉における燃料集合体１の除熱性能を把握するには、このような高温・高圧の条件で燃料棒２の表面を流れる沸騰二相流を分析しなければならず、しかも、前述の如く、スペーサ４の近傍では、更に複雑な流れが形成されると考えられるところ、仮に、このような高温・高圧の実機条件を再現する電気加熱式試験機等を使用し得たとしても、試験機内に生じる沸騰二相流の流動様相を観察し又は測定することは、現在の計測技術では、極めて困難であり、高温・高圧の実機内で沸騰二相流が実際にどのような挙動を示すのかについて観察し又は測定することはできない。   However, under the general design conditions of a boiling water reactor (actual machine), the internal environment of the fuel assembly 1 reaches a pressure of 7 MPa and a temperature of 285 ° C. Therefore, in order to grasp the heat removal performance of the fuel assembly 1 in the boiling water reactor, the boiling two-phase flow flowing on the surface of the fuel rod 2 under such high temperature and high pressure conditions must be analyzed. In addition, as described above, it is considered that a more complicated flow is formed in the vicinity of the spacer 4, but it was possible to use an electric heating type testing machine or the like that reproduces such high temperature and high pressure actual machine conditions. However, it is extremely difficult to observe or measure the flow behavior of the boiling two-phase flow generated in the test machine with the current measurement technology. It is not possible to observe or measure whether it behaves correctly.

他方、このような沸騰二相流の流動現象又は流動様相を支配する支配因子は、気相と液相のそれぞれの流体物性、殊に、密度、表面張力、粘度であると考えられる。従って、これらの物性の絶対値が、実機の沸騰二相流における気相と液相のそれぞれの流体物性（密度、表面張力、粘度）の絶対値と実質同一又は同等であれば、観察可能且つ測定可能な常温・低圧条件の環境であっても、実機の燃料集合体１に発生する沸騰二相流の流動様相を模擬し、高温・高圧の実機内に発生する熱流動現象を擬似的に再現し得ると考えられる。   On the other hand, the controlling factors governing the flow phenomenon or flow aspect of such boiling two-phase flow are considered to be the fluid physical properties of the gas phase and the liquid phase, in particular, the density, surface tension and viscosity. Therefore, if the absolute values of these physical properties are substantially the same as or equivalent to the absolute values of the fluid physical properties (density, surface tension, viscosity) of the gas phase and the liquid phase in the boiling two-phase flow of the actual machine, they can be observed and Simulates the flow behavior of the boiling two-phase flow generated in the fuel assembly 1 of the actual machine and simulates the heat flow phenomenon generated in the high-temperature and high-pressure actual machine even in a measurable room temperature / low pressure environment It can be reproduced.

図５（Ａ）には、大気圧及び実機圧力（70atm)における水の諸物性が夫々示されている。   FIG. 5A shows various physical properties of water at atmospheric pressure and actual machine pressure (70 atm).

図５（Ａ）に物性値として示すように、水の大気圧下の飽和温度（100 ℃）における諸物性は、高温・高圧（圧力7MPa、温度285 ℃）下における水の諸物性とは、大きく相違する。従って、観察可能且つ測定可能な常温・常圧条件の環境で水を用いて沸騰二相流を形成したとしても、実機内の熱流動現象を擬似的に再現することはできず、仮にこれを行ったとしても、燃料集合体１における除熱性能の予測精度は低く、現状では実用の域に達しない。   As shown in FIG. 5A as physical property values, the physical properties of water at the saturation temperature (100 ° C) under atmospheric pressure are the physical properties of water at high temperature and high pressure (pressure 7MPa, temperature 285 ° C). It is very different. Therefore, even if a boiling two-phase flow is formed using water in an observable and measurable environment of normal temperature and normal pressure, the heat flow phenomenon in the actual machine cannot be reproduced in a pseudo manner. Even if it is performed, the prediction accuracy of the heat removal performance in the fuel assembly 1 is low, and it does not reach the practical range at present.

図５（Ｂ）には、実機条件（70atm)における水の諸物性と、エタノール及びHFC134a ガスの諸物性が、物性値として示されている。   FIG. 5B shows physical properties of water and physical properties of ethanol and HFC134a gas under actual machine conditions (70 atm).

常温・低圧の環境において気体及び液体を混合して二相流体を形成した場合、両者の化学反応が進行しないと仮定すると、適切に選択して組み合わせた気体及び液体の二相流体は、気体及び液体の夫々の諸物性のうち二相流体の性質を実質的に支配する物性を適当に利用することにより、高温・高圧の沸騰二相流体の挙動を疑似することができる。本実施形態においては、沸騰水型原子炉の高温・高圧（圧力7MPa、温度285 ℃）の環境で発生する沸騰二相流を常温・低圧の環境で再現するための液体及び気体として、エタノール及びHFC134a ガスが採用される。   When a gas and liquid are mixed to form a two-phase fluid in a room temperature / low pressure environment, assuming that the chemical reaction between the two does not proceed, the gas and liquid two-phase fluid appropriately selected and combined are By appropriately utilizing the physical properties that substantially control the properties of the two-phase fluid among the various physical properties of the liquid, it is possible to simulate the behavior of a high-temperature and high-pressure boiling two-phase fluid. In the present embodiment, ethanol and ethanol are used as a liquid and a gas for reproducing a boiling two-phase flow generated in a high temperature / high pressure (pressure 7 MPa, temperature 285 ° C.) environment of a boiling water reactor in a normal temperature / low pressure environment. HFC134a gas is used.

液体模擬物質としてエタノールを用い、蒸気模擬物質としてHFC134a ガスを用いた場合、これら二つの物質を混合した二相流体の密度、表面張力及び粘度は、高温・高圧（圧力7MPa、温度285 ℃）の環境に発生する沸騰二相流の密度、表面張力及び粘度と類似する。従って、エタノール及びHFC134a ガスを混合した二相流体によって上述の沸騰二相流を疑似することにより、高温高圧条件（圧力7MPa、温度285 ℃）の気液二相流動現象を観察可能且つ計測可能な常温・低圧の条件で再現することができる。   When ethanol is used as the liquid simulation substance and HFC134a gas is used as the vapor simulation substance, the density, surface tension, and viscosity of the two-phase fluid mixed with these two substances are high and high pressure (pressure 7MPa, temperature 285 ° C). Similar to the density, surface tension and viscosity of the boiling two-phase flow generated in the environment. Therefore, by simulating the above boiling two-phase flow with a two-phase fluid mixed with ethanol and HFC134a gas, gas-liquid two-phase flow phenomena under high temperature and high pressure conditions (pressure 7MPa, temperature 285 ° C) can be observed and measured. Can be reproduced under normal temperature and low pressure conditions.

即ち、高温・高圧の環境に存在する沸騰二相流の流れの特性を支配する物性を特定し、この物性の物性値と同等又は同程度の物性値を常温・低圧の環境で保有する気体及び液体を適切に組合せた二相流体を形成し、この二相流体を擬似的な沸騰二相流として使用し、これにより、高温高圧条件の沸騰二相流の液膜挙動を観察可能且つ計測可能な常温・低圧の環境で再現することができる。   That is, the physical properties that govern the characteristics of the boiling two-phase flow existing in a high-temperature and high-pressure environment are identified, and the gas possessing a physical property value equivalent to or similar to the physical property value of this physical property in a normal-temperature and low-pressure environment and Forming a two-phase fluid with an appropriate combination of liquids, and using this two-phase fluid as a simulated boiling two-phase flow, it is possible to observe and measure the liquid film behavior of a boiling two-phase flow under high temperature and high pressure conditions It can be reproduced in a normal room temperature and low pressure environment.

このような方法によれば、高温・高圧の沸騰二相流を用いた装置の設計・開発に要するコストを大幅に削減するとともに、開発期間をかなり短縮することができる。殊に、原子炉は、発電量が非常に大きいことから、限界出力を僅か１％向上させることができれば、莫大な利益につながるので、本発明の模擬方法を原子力の設計・開発に適用し、限界出力を高精度に設定して燃料集合体を最適化し、１％程度の性能向上を図ることができた場合、電力会社が所有する100 万kW級の原子炉では、1 万kW程度、更に発電することができ、これを現在の物価で経済効果として試算すると、１ヶ月で約1.5 億円（22円／1kWhとして試算）、１年で18億円の経済効果が得られる。   According to such a method, the cost required for the design and development of the apparatus using the high-temperature and high-pressure boiling two-phase flow can be greatly reduced, and the development period can be considerably shortened. In particular, since the power generation amount of a nuclear reactor is very large, if the limit power can be improved by only 1%, it will lead to enormous profits. Therefore, the simulation method of the present invention is applied to the design and development of nuclear power, If you can optimize the fuel assembly by setting the critical power with high accuracy and improve the performance by about 1%, the 1 million kW class nuclear reactor owned by the power company will have about 10,000 kW. It is possible to generate electricity, and if this is estimated as an economic effect at the current price, it will cost approximately 150 million yen per month (estimated as 22 yen / 1 kWh), and an economic effect of 1.8 billion yen per year.

常温・低圧、例えば、大気温（又は室温）且つ大気圧、或いは、通常の実験機器で容易に形成可能な温度及び圧力の環境の下で上記二相流体（エタノール及びHFC134a ガス）を供給する流体供給手段と、この二相流体が供給される直線流路とを備えた熱流動現象の模擬試験装置を本発明に従って設計することができる。   A fluid that supplies the above two-phase fluid (ethanol and HFC134a gas) under normal temperature and low pressure, for example, atmospheric temperature (or room temperature) and atmospheric pressure, or an environment of temperature and pressure that can be easily formed by ordinary laboratory equipment. A simulation test apparatus for a thermal fluid phenomenon including a supply means and a straight channel through which the two-phase fluid is supplied can be designed according to the present invention.

図６は、本発明の実施例に係る模擬試験装置の構成を概略的に示す断面図である。   FIG. 6 is a cross-sectional view schematically showing the configuration of the simulation test apparatus according to the embodiment of the present invention.

試験装置は、液体及び気体を混合する気液混合器２０と、液体及び気体を分離する気液分離器３０と、液体及び気体の混合気が流通する管体４０とを備える。管体４０は垂直に配置される。気液混合器２０は管体４０の下端部に配置され、気液分離器３０は管体４０の上端部に配置される。   The test apparatus includes a gas-liquid mixer 20 that mixes liquid and gas, a gas-liquid separator 30 that separates liquid and gas, and a tube body 40 through which a mixture of liquid and gas flows. The tube body 40 is disposed vertically. The gas-liquid mixer 20 is disposed at the lower end portion of the tube body 40, and the gas-liquid separator 30 is disposed at the upper end portion of the tube body 40.

HFC134a ガスを供給する気体供給管２１（破線で示す）が、気液混合器２０の気体流入ポート２２に接続される。気体供給管２１は、気体給送手段（図示せず）を介して管HFC134a ガスのガス発生器（図示せず）に接続される。エタノール液を供給する液体供給管２３（破線で示す）が、気液混合器２０の液体流入ポート２４に接続される。液体供給管２３は、液体給送手段（図示せず）を介してエタノール液の貯留槽（図示せず）に接続される。   A gas supply pipe 21 (shown by a broken line) for supplying HFC134a gas is connected to the gas inflow port 22 of the gas-liquid mixer 20. The gas supply pipe 21 is connected to a gas generator (not shown) of pipe HFC134a gas via a gas feeding means (not shown). A liquid supply pipe 23 (shown by a broken line) for supplying ethanol liquid is connected to the liquid inflow port 24 of the gas-liquid mixer 20. The liquid supply pipe 23 is connected to an ethanol liquid storage tank (not shown) via a liquid feeding means (not shown).

HFC134a ガスをガス発生器に還流させる気体回収管３１（破線で示す）が気液分離器３０の気体流出ポート３２に接続される。気体回収管３１は、気体還流手段（図示せず）を介してガス発生器に接続される。エタノール液を液槽に還流する液体回収管３３（破線で示す）が、気液分離器の液体流出ポート３４に接続される。液体回収管３３は、液体還流手段及び液膜流量検出手段（図示せず）を介してエタノール液の貯留槽に接続される。液膜流量検出手段は、液体回収管３３によって回収される液量（エタノール液量）の時間変化を検出する液量計を有する。   A gas recovery pipe 31 (represented by a broken line) for refluxing the HFC134a gas to the gas generator is connected to the gas outflow port 32 of the gas-liquid separator 30. The gas recovery pipe 31 is connected to a gas generator through a gas reflux means (not shown). A liquid recovery pipe 33 (shown by a broken line) for returning the ethanol liquid to the liquid tank is connected to the liquid outflow port 34 of the gas-liquid separator. The liquid recovery pipe 33 is connected to an ethanol liquid storage tank via liquid reflux means and liquid film flow rate detection means (not shown). The liquid film flow rate detection means has a liquid meter that detects a change in the amount of liquid (ethanol liquid amount) recovered by the liquid recovery pipe 33 over time.

管体４０は、HFC134a及びエタノールの気液混合気Ｆが流通可能な円形断面の垂直流路４１を有する。流路４１の下端部は、気液混合器２０の流出ポート２５に接続され、流路４１の上端部は、気液分離器３０の流入ポート３５に接続される。   The tubular body 40 has a vertical flow path 41 having a circular cross section through which a gas-liquid mixture F of HFC134a and ethanol can flow. The lower end portion of the flow path 41 is connected to the outflow port 25 of the gas-liquid mixer 20, and the upper end portion of the flow path 41 is connected to the inflow port 35 of the gas-liquid separator 30.

試験装置は、流路壁４２上の液膜の膜厚を計測するための膜厚計測手段を備える。空気・水系のシステムにおいて非接触で気液比及び液膜厚さを測定する手法として定電圧法及び定電流法が知られているが、本実施例においては、センサ間の干渉がなく、しかも、膜厚の減少に対して出力を増大する（従って、計測精度が高い）定電流法が採用される。膜厚計測手段は、流路方向に間隔を隔てた流路壁４２の２点間電位差を夫々測定する上流側及び下流側の電圧計（Ｖ）と、各電圧計（Ｖ）の計測値を記録するデータレコーダ（ＤＲ）とを備える。直流電源に接続された正負の電極対４５が、管体４０の上部及び下部に夫々挿入され、流路壁４２の液膜に通電する。各電圧計（Ｖ）の検知電極対４６が、流路壁４２の所定位置において流路壁４２上の液膜に接触するように配置される。管体４０は、非導電性樹脂等によって全体的に形成され、定電流電源の電力を印加する電極対４５と、液膜厚さ検知用の電極対４６のみが金属によって形成される。   The test apparatus includes a film thickness measuring means for measuring the film thickness of the liquid film on the flow path wall 42. The constant voltage method and the constant current method are known as methods for measuring the gas-liquid ratio and the liquid film thickness in a non-contact manner in an air / water system. However, in this embodiment, there is no interference between sensors, and A constant current method is employed in which the output is increased (thus, the measurement accuracy is high) with respect to the decrease in film thickness. The film thickness measuring means includes an upstream voltmeter (V) for measuring a potential difference between two points of the flow path wall 42 spaced in the flow path direction, and a measured value of each voltmeter (V). A data recorder (DR) for recording. Positive and negative electrode pairs 45 connected to a DC power source are respectively inserted into the upper and lower portions of the tube body 40 and energize the liquid film on the flow path wall 42. The detection electrode pair 46 of each voltmeter (V) is disposed so as to contact the liquid film on the flow path wall 42 at a predetermined position of the flow path wall 42. The tube 40 is entirely formed of a non-conductive resin or the like, and only the electrode pair 45 for applying the power of the constant current power source and the electrode pair 46 for detecting the liquid film thickness are formed of metal.

試験装置は更に、差圧センサ（ＤＰ）を有し、差圧センサ（ＤＰ）の検知部４３が流路４１に設置される。検知部４３は、流路４１の流入部及び流出部に夫々配置され、金属管４９によって差圧センサ本体に接続される。金属管４９には、圧力信号を差圧センサ本体に伝達する液体が充填され、差圧センサ（ＤＰ）は、流路４１の流入部及び流出部における二相流体の圧力差を検出する。このような差圧検出により、原子炉ポンプの容量や必要性能の設定に必要な流体圧損データが得られる。   The test apparatus further includes a differential pressure sensor (DP), and a detection unit 43 of the differential pressure sensor (DP) is installed in the flow path 41. The detection unit 43 is disposed at each of the inflow portion and the outflow portion of the flow path 41 and is connected to the differential pressure sensor main body by a metal tube 49. The metal tube 49 is filled with a liquid that transmits a pressure signal to the differential pressure sensor body, and the differential pressure sensor (DP) detects the pressure difference between the two-phase fluids at the inflow portion and the outflow portion of the flow path 41. Such differential pressure detection provides fluid pressure loss data necessary for setting the capacity and required performance of the reactor pump.

図７は、図６に示す試験装置を用いて実施した液膜挙動再現実験の実験結果を示す線図である。   FIG. 7 is a diagram showing the experimental results of a liquid film behavior reproduction experiment conducted using the test apparatus shown in FIG.

液膜挙動再現実験において、エタノール及びHFC134a ガスの二相流体が気液混合器２０から流路４１内に連続的に給送された。二相流体は、流路４１を上昇して気液分離器３０に流出する。上下の電圧計（Ｖ）によって、計測点α、βにおける電位差が夫々計測され、データレコーダ（ＤＲ）に記録された。計測点α、βにおいて夫々計測された電位差の値は、下式により、流路壁４２に形成された液膜の膜厚値に変換された。

Figure 0004863414
In the liquid film behavior reproduction experiment, a two-phase fluid of ethanol and HFC134a gas was continuously fed into the channel 41 from the gas-liquid mixer 20. The two-phase fluid moves up the flow path 41 and flows out to the gas-liquid separator 30. The potential difference at the measurement points α and β was measured by the upper and lower voltmeters (V) and recorded in the data recorder (DR). The value of the potential difference measured at each of the measurement points α and β was converted into the film thickness value of the liquid film formed on the flow path wall 42 by the following equation.
Figure 0004863414

なお、上式における各符号は、以下の数値を夫々示す。
d :管内径
d0 :検定棒外径
V0 :検定棒挿入時の出力電圧
I0 ：検定棒挿入時の定電流値
VTP : 膜厚測定時の出力電圧
I ：膜厚測定時の定電流値 In addition, each code | symbol in the above type | formula shows the following numerical values, respectively.
d: Pipe inner diameter
d 0 : Test rod outer diameter
V 0 : Output voltage when test rod is inserted
I 0 : Constant current value when the test rod is inserted
V TP : Output voltage during film thickness measurement
I: Constant current value during film thickness measurement

図７（Ａ）及び図７（Ｂ）は、エタノール及びHFC134aの流量が異なる二つの実験の各実験結果を示す線図である。図７（Ａ）及び図７（Ｂ）には、計測点α、βにおける膜厚の時間変化が示されている。図７において、符号JGは、流路４１を気相が充満して流れたと仮定して求められた見かけの速度であり、符号JL は、同様に流路４１を液相が充満して流れたと仮定して求められた見かけの速度を示す。また、符号τiは，気液界面のせん断応力であり、次式で定義される。符号Δtは、上下流の膜厚データの相互相関係数の最大値として得られる２つの波形の時刻のずれ時間であり、符号vDWは、センサ間の距離（57mm）をΔtで除すことにより算定されるじょう乱波速度を示す。

Figure 0004863414
FIG. 7A and FIG. 7B are diagrams showing the results of two experiments in which the flow rates of ethanol and HFC134a are different. FIGS. 7A and 7B show changes in film thickness over time at the measurement points α and β. In FIG. 7, the symbol J G is an apparent speed obtained on the assumption that the gas phase is filled in the flow path 41, and the symbol J L is the same as that in the flow path 41 when the liquid phase is filled. The apparent speed obtained on the assumption that it has flowed is shown. Symbol τ i is a shear stress at the gas-liquid interface and is defined by the following equation. The sign Δt is the time lag time between two waveforms obtained as the maximum value of the cross-correlation coefficient of the upstream and downstream film thickness data, and the sign v DW is obtained by dividing the distance (57 mm) between the sensors by Δt. The disturbance wave velocity calculated by
Figure 0004863414

計測点α、βは、鉛直方向に所定距離（本例では、距離約57mm）を隔てており、流路壁４２の内壁面に形成された液膜は、波状形態をなして下流側に遷移することから、上流側の計測点αに生じた膜厚変化と類似な膜厚変化が、下流側の計測点βにおいて所定時間Δｔ後に現れる．   The measurement points α and β are separated from each other by a predetermined distance (in this example, a distance of about 57 mm) in the vertical direction, and the liquid film formed on the inner wall surface of the flow path wall 42 forms a wavy shape and transitions downstream. Therefore, a film thickness change similar to the film thickness change generated at the upstream measurement point α appears after a predetermined time Δt at the downstream measurement point β.

図７（Ａ）及び図７（Ｂ）には、計測点α、βにおける膜厚変化が夫々示されている。各図において、計測点βの膜厚変化と計測点αの膜厚変化とを容易に対比し得るように、計測点βの膜厚変化は、その位相を時間Δｔだけ変移させた状態で示されている。   7A and 7B show changes in film thickness at the measurement points α and β, respectively. In each figure, the film thickness change at the measurement point β is shown with its phase shifted by time Δt so that the film thickness change at the measurement point β can be easily compared with the film thickness change at the measurement point α. Has been.

図７（Ａ）及び図７（Ｂ）に示すように、実質的に同一の膜厚変化が時間差Δｔで計測点α、βに顕れており、沸騰二相流の流動現象を再現するエタノール及びHFC134a ガスの二相流体の場合においても、測定上の矛盾がないことが確認された。   As shown in FIGS. 7A and 7B, substantially the same change in film thickness appears at the measurement points α and β with a time difference Δt, and ethanol that reproduces the flow phenomenon of boiling two-phase flow and Even in the case of the two-phase fluid of HFC134a gas, it was confirmed that there was no contradiction in measurement.

図８は、サブチャンネル解析コード(NASCA)による解析結果と、液膜挙動再現実験の実験結果とを示す線図である。図８(A)には、気相の見かけ流速と、液膜流量との関係が示され、図８(B)には、気相の見かけ流速と、液膜厚さとの関係が示されている。   FIG. 8 is a diagram showing the analysis result by the subchannel analysis code (NASCA) and the experimental result of the liquid film behavior reproduction experiment. FIG. 8 (A) shows the relationship between the apparent flow rate in the gas phase and the liquid film flow rate, and FIG. 8 (B) shows the relationship between the apparent flow rate in the gas phase and the liquid film thickness. Yes.

図８に示す如く、エタノール及びHFC134a ガスの流量に応じて、流路４１内の気体流速（JG）は増大し、流路壁４２の内壁面に形成される液膜の膜厚(tFm)は変化する。再現実験の計測値は、液膜流量（図８(A)）及び液膜厚さ（図８(B)）の双方において、サブチャンネル解析コード(NASCA)による解析結果と極めて類似する。ここに、サブチャンネル解析コード(NASCA)は、スペーサが設けられない場合には、液膜挙動を精度良く再現できる。上記模擬試験装置により測定した液膜流量及び液膜厚さの双方が、そのようなサブチャンネル解析コード(NASCA)の解析結果と極めて良く一致することは、本手法の妥当性が確認されたことを意味する。即ち、本実施例によれば、主要な物性値が高温高圧下の水及び蒸気と同程度である液体（エタノール）及び気体(HFC134a)を作動流体(実験圧力: 0.7MPa，実験温度：27℃)として使用し、高温高圧の蒸気−水系の二相流動を直線流路４１において生じさせることにより、液膜厚さ、液膜流量及び圧力損失を測定可能な高温高圧下の二相流動を模擬することができる。 As shown in FIG. 8, the gas flow velocity (J G ) in the flow path 41 increases according to the flow rates of ethanol and HFC134a gas, and the film thickness (t Fm) of the liquid film formed on the inner wall surface of the flow path wall 42 is increased. ) Will change. The measurement value of the reproduction experiment is very similar to the analysis result by the subchannel analysis code (NASCA) in both the liquid film flow rate (FIG. 8A) and the liquid film thickness (FIG. 8B). Here, the subchannel analysis code (NASCA) can accurately reproduce the liquid film behavior when no spacer is provided. The validity of this method was confirmed that both the liquid film flow rate and the liquid film thickness measured by the above-mentioned simulation test apparatus are in good agreement with the analysis results of such a subchannel analysis code (NASCA). Means. That is, according to this example, liquid (ethanol) and gas (HFC134a) whose main physical property values are similar to water and steam under high temperature and high pressure are used as working fluid (experimental pressure: 0.7 MPa, experimental temperature: 27 ° C. ) And a two-phase flow of a high-temperature and high-pressure steam-water system is generated in the straight flow path 41, thereby simulating a two-phase flow under a high temperature and high pressure that can measure the liquid film thickness, the liquid film flow rate and the pressure loss. can do.

沸騰水型原子炉（ＢＷＲ）の開発・設計においては、開発から実証に至る過程で試験・実験的アプローチが重視されてきたが、近年の沸騰水型原子炉や、次世代の沸騰水型原子炉では、燃料の大型化や、格子稠密化等の理由により、試験・実験的アプローチの採用が実験機器容量や開発コスト等との関係で困難になりつつあり、試験・実験に依存した開発・設計から解析中心の開発・設計に移行することが望まれている。しかしながら、スペーサ廻りの乱流解析や、燃料バンドルにおける気液クロスフロー効果等については、サブチャンネル解析コード(NASCA)による解析では、得られない。しかしながら、図６に示す試験装置によれば、スペーサを模擬する障害物を流路４１内に配置して前述の液膜挙動再現実験を実施し、これにより、スペーサが液膜挙動に与える影響を分析し、サブチャンネル解析コード(NASCA)に適用可能なスペーサ増倍係数等を設定することができる。   In the development and design of boiling water reactors (BWRs), testing and experimental approaches have been emphasized in the process from development to demonstration, but in recent years boiling water reactors and next-generation boiling water reactors In the reactor, the adoption of testing / experimental approaches is becoming difficult due to factors such as the increase in fuel size and grid density, due to factors such as the capacity of experimental equipment and development costs. It is desired to shift from design to analysis-centric development and design. However, the turbulent flow analysis around the spacer and the gas-liquid cross-flow effect in the fuel bundle cannot be obtained by the analysis using the subchannel analysis code (NASCA). However, according to the test apparatus shown in FIG. 6, an obstacle that simulates the spacer is placed in the flow channel 41 and the above-described liquid film behavior reproduction experiment is performed. It is possible to analyze and set a spacer multiplication factor applicable to the subchannel analysis code (NASCA).

以上、本発明の好適な実施形態について詳細に説明したが、本発明は上記実施形態に限定されるものではなく、特許請求の範囲に記載された本発明の範囲内で種々の変形又は変更が可能である。   The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above-described embodiments, and various modifications or changes can be made within the scope of the present invention described in the claims. Is possible.

例えば、試験装置の流路断面は、必ずしも全長に亘る均等又は均一な円形断面に限定されるものではなく、流路断面を楕円形断面、多角形断面等に設計し、或いは、流路断面を適当に変化させても良い。   For example, the flow channel cross section of the test apparatus is not necessarily limited to a uniform or uniform circular cross section over the entire length, and the flow channel cross section is designed to be an elliptical cross section, a polygonal cross section, etc. It may be changed appropriately.

また、試験装置の管体を流通する二相流体の視覚的な観察を可能にするように管体を透明又は半透明の素材で形成することも可能である。   It is also possible to form the tube with a transparent or translucent material so as to allow visual observation of the two-phase fluid flowing through the tube of the test apparatus.

更に、上記実施例では、定電流法を用いて液膜の膜厚を測定しているが、膜厚測定に定電圧法を採用し、或いは、レーザー光によって液膜の膜厚を測定する非接触型の光学式膜厚測定装置等を使用した光学的測定法を採用しても良い。   Furthermore, in the above embodiment, the film thickness of the liquid film is measured using the constant current method, but the constant voltage method is adopted for the film thickness measurement, or the film thickness of the liquid film is measured by laser light. An optical measurement method using a contact-type optical film thickness measuring device or the like may be employed.

本発明の模擬方法及び模擬試験装置は、沸騰水型原子炉（ＢＷＲ型原子炉）の開発から実証に至る過程において、燃料棒の限界出力を設定するための試験又は実験に使用される。本発明の模擬方法及び模擬試験装置によって得られた液膜挙動の情報に基づいて、燃料棒表面の液膜挙動に対するスペーサの影響等の如く、燃料棒の除熱性能に大きく影響を与える因子を定量的に評価することが可能となる。これは、沸騰水型原子炉内の熱流動現象を解析する上で必要な未知データの取得を可能にし、サブチャンネル解析コード(NASCA)の精度向上に大きく寄与すると考えられ、その実用的価値は、顕著である。   The simulation method and the simulation test apparatus of the present invention are used for a test or experiment for setting a limit output of a fuel rod in a process from the development to the demonstration of a boiling water reactor (BWR reactor). Based on the information on the liquid film behavior obtained by the simulation method and simulation test apparatus of the present invention, factors that greatly affect the heat removal performance of the fuel rod, such as the influence of the spacer on the liquid film behavior on the fuel rod surface, etc. It becomes possible to evaluate quantitatively. This enables the acquisition of unknown data necessary for analyzing the thermal flow phenomena in boiling water reactors, and is considered to contribute greatly to improving the accuracy of the subchannel analysis code (NASCA). Is remarkable.

燃料集合体の構成を部分的に示す正面図及び横断面図である。It is the front view and transverse cross section which show the structure of the fuel assembly partially. 燃料棒の管壁を部分的に拡大して示す部分拡大断面図である。It is a partial expanded sectional view which expands and shows the pipe wall of a fuel rod partially. スペーサの近傍に生じる液膜挙動を例示する部分拡大断面図である。It is a partial expanded sectional view which illustrates the liquid film behavior which arises near the spacer. 燃料棒を模擬した発熱管上に生じる液膜の膜厚変動特性を示す線図である。It is a diagram which shows the film thickness fluctuation | variation characteristic of the liquid film produced on the heat generating pipe which simulated the fuel rod. 図４（Ａ）は、大気圧及び実機圧力（70atm)における水の諸物性を示す図表であり、図４（Ｂ）は、実機条件（70atm)における水の諸物性と、エタノール及びHFC134a ガスの諸物性を示す図表である。Fig. 4 (A) is a chart showing various physical properties of water at atmospheric pressure and actual machine pressure (70atm). Fig. 4 (B) shows various physical properties of water under actual machine conditions (70atm), ethanol and HFC134a gas. It is a chart which shows various physical properties. 本発明の実施例に係る模擬試験装置の構成を概略的に示す断面図である。It is sectional drawing which shows roughly the structure of the simulation test apparatus based on the Example of this invention. 図６に示す試験装置を用いて実施した液膜挙動再現実験の実験結果を示す線図である。It is a diagram which shows the experimental result of the liquid film behavior reproduction experiment implemented using the test apparatus shown in FIG. 気相の見掛け速度と液膜流量及び平均液膜厚さとの関係を示す線図である。It is a diagram which shows the relationship between the apparent velocity of a gaseous phase, a liquid film flow volume, and an average liquid film thickness.

符号の説明Explanation of symbols

１ 燃料集合体
２ 燃料棒
３ スペーサ
４ 間隙
５ 管壁
１０ 液膜
１１ じょう乱波
１２ 液膜ドライアウト現象
２０ 気液混合器
３０ 気液分離器
４０ 管体
４１ 流路
４２ 流路壁
DESCRIPTION OF SYMBOLS 1 Fuel assembly 2 Fuel rod 3 Spacer 4 Gap 5 Tube wall 10 Liquid film 11 Disturbance wave 12 Liquid film dryout phenomenon 20 Gas-liquid mixer 30 Gas-liquid separator 40 Tube 41 Channel 42 Channel wall

Claims (6)

沸騰水型原子炉内の高温・高圧環境に存在する沸騰二相流の熱流動現象を再現する熱流動現象の模擬方法において、
前記沸騰二相流の密度、表面張力及び粘度の物性値と実質的に同一又は同等の密度、表面張力及び粘度の物性値を常温・低圧の環境で示す二相流体の流れを液体及び気体の混合流体によって形成し、
前記二相流体を所定断面且つ常温・低圧の直線流路に通して、該流路の流路壁面に液膜を形成し、高温・高圧の環境で前記沸騰二相流が前記沸騰水型原子炉の燃料棒の伝熱表面に形成する液膜を常温・低圧の環境で流路壁面に再現して該液膜の挙動を模擬し、
前記液膜の膜厚及び／又は液膜流量を測定することを特徴とする熱流動現象の模擬方法。 In the simulation method of heat flow phenomenon that reproduces the heat flow phenomenon of boiling two-phase flow existing in high temperature and high pressure environment in boiling water reactor,
The flow of a two-phase fluid showing the physical properties of density, surface tension and viscosity substantially the same or equivalent to the physical properties of density, surface tension and viscosity of the boiling two-phase flow in a normal temperature / low pressure environment. Formed by a mixed fluid,
The two-phase fluid is passed through a straight channel having a predetermined cross section and a normal temperature / low pressure, and a liquid film is formed on the channel wall surface of the channel, and the boiling two-phase flow is generated in the boiling water atom in a high temperature / high pressure environment. The liquid film formed on the heat transfer surface of the fuel rod of the furnace is reproduced on the wall surface of the flow path in a normal temperature / low pressure environment to simulate the behavior of the liquid film,
A method for simulating a thermal fluid phenomenon, comprising measuring a film thickness and / or a liquid film flow rate of the liquid film. 前記液体は、エタノールであり、前記気体は、HFC134a ガスであることを特徴とする請求項１に記載の熱流動現象の模擬方法。   The method for simulating a thermal fluid phenomenon according to claim 1, wherein the liquid is ethanol and the gas is HFC134a gas. 流路方向に間隔を隔てた複数の計測点において液膜の膜厚を電気抵抗法又は光学的測定法によって計測することを特徴とする請求項１又は２に記載の熱流動現象の模擬方法。   3. The method of simulating a thermal fluid phenomenon according to claim 1, wherein the film thickness of the liquid film is measured by an electric resistance method or an optical measurement method at a plurality of measurement points spaced in the flow path direction. 請求項１乃至３のいずれか１項に記載の模擬方法によって限界出力を最適化した燃料集合体を有することを特徴とする沸騰水型原子炉。   A boiling water nuclear reactor comprising a fuel assembly having a limit output optimized by the simulation method according to any one of claims 1 to 3. 沸騰水型原子炉内の高温・高圧環境に存在する沸騰二相流の熱流動現象を再現する熱流動現象の模擬試験装置において、
前記沸騰二相流の密度、表面張力及び粘度の物性値と実質的に同一又は同等の密度、表面張力及び粘度の物性値を常温・低圧の環境で示す二相流体が供給される常温・低圧の直線流路と、
前記二相流体を形成する液体及び気体の混合流体を前記直線流路に供給する流体供給手段と、
前記混合流体によって前記直線流路の流路壁面に形成された液膜の膜厚及び／又は液膜流量を測定する液膜計測手段とを備え、
前記沸騰水型原子炉の燃料棒の伝熱表面に形成される液膜を常温・低圧の環境で前記流路壁面に再現して前記液膜の挙動を模擬するとともに、前記液膜の膜厚及び／又は液膜流量を測定するようにしたことを特徴とする熱流動現象の模擬試験装置。 In a thermal fluid phenomenon simulation test device that reproduces the thermal fluid phenomenon of a boiling two-phase flow existing in a high temperature and high pressure environment in a boiling water reactor,
Normal temperature / low pressure at which a two-phase fluid is supplied that exhibits physical properties of density, surface tension and viscosity substantially the same or equivalent to the physical properties of density, surface tension and viscosity of the boiling two-phase flow. A straight channel of
Fluid supply means for supplying a fluid mixture of liquid and gas forming the two-phase fluid to the linear flow path;
A liquid film measuring means for measuring the film thickness and / or the liquid film flow rate of the liquid film formed on the flow channel wall surface of the linear flow channel by the mixed fluid,
The liquid film formed on the heat transfer surface of the fuel rod of the boiling water reactor is reproduced on the wall surface of the flow path in a room temperature / low pressure environment to simulate the behavior of the liquid film, and the film thickness of the liquid film And / or a thermal fluid phenomenon simulation test apparatus characterized by measuring a liquid film flow rate. 前記液膜計測手段は、流路方向に所定間隔を隔てた複数の計測点において液膜の膜厚を電気抵抗法又は光学的測定法によって計測する膜厚計測装置を備えることを特徴とする請求項５に記載の模擬試験装置。

The liquid film measuring means includes a film thickness measuring device that measures the film thickness of the liquid film by an electrical resistance method or an optical measurement method at a plurality of measurement points spaced at predetermined intervals in the flow path direction. Item 6. The simulation test apparatus according to Item 5.

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