報告書番号

U93005

タイトル（和文）

ＦＢＲ炉内自然循環現象の熱流動相似則の検討－その２

タイトル（英文）

INVESTIGATION OF SIMILARITY RULE FOR NATURALCIRCULATION EXPERIMENT IN AN LMFBR-PART2

概要 （図表や脚注は「報告書全文」に掲載しております）

ＦＢＲの自然循環現象を実験から実機を予測するための相似則はまだ一般化されていない。これまでの研究により自然循環現象を支配するパラメータとして，Ｂｏ’数，Ｇｒ’数が重要であることが明らかとなった。ここでは，実機形状を模擬した二つの実験装置（１／２０模型と１／６模型）を用いて，実験を行った。流速変化を調べることにより，Ｇｒ’数の効果は，十分に緩和されていることが分かった。また，温度変化を調べることにより，Ｂｏ’数が小さい領域では，Ｂｏ’数の効果が，現象に現れることが分かった。なお，実機でのＢｏ’数は，今回の実験で行った低Ｂｏ’数の範囲に近いと予想されるため，実機の現象を模擬した実験を行う際は，注意を払う必要があると考えられる。さらに，１／６模型を用いて，炉内の熱流動現象の特性（温度成層化，温度ゆらぎ）を把握した。

概要 （英文）

REMOVAL OF DECAY HEAT BY NATURAL CIRCULATIONWILL BE INTRODUCED IN OPERATION OF LMFBRS. NATURAL CIRCULATION IS HIGHLY RELIABLE,BUT IS UNSTABLE AND SUBTLE,WHICH MAKES FINE PREDICTION DIFFICULT. THE PHENOMENA ARE GOVERNED BY A DELICATE BALANCE BETWEEN THE BUOYANCY FORCE AND THE LOW PRESSURE LOSS AND ARE INFLUENCED BY VARIOUS PARAMETERS SUCH AS LOCAL GEOMETRY,AND HEAT CAPACITY. THEREFORE THE SIMILARITY RULE FOR NATURAL CIRCULATION IS NOT FULLY UNDER STOOD. THIS STUDY WAS CONDUCTED TO ESTABLISH A SIMULATION METHOD FOR NATURAL CIRCULATION PHENOMENA AND THE PHENOMENA HAVE BEEN REVIEWED IN DETAIL. THERE ARE NO READILY AVAILABLE REFERENCE VELOCITY AND TEMPERATURE. DATA FOR NATURAL CIRCULATION IN AN LMFBR. THESE VALUES ARE RELATED TO THE HEATING AND COOLING RATE,THE CHARACTERISTIC LEGTHS AND PHYSICAL PROPERTIES OF THE TESTFLUID. BASIC EQUATIONS WERE TRANSFORMED TO THESE VALUES,DIMENSIONLESS EQUATIONS WERE DERIVED AND THEN TWO-DIMENSIONLESS NUMBERS,THE GR NUMBERAND THE BO NUMBER WERE IDENTIFIED. TO EXAMINE THE SIMILARITY RULE FOR NATURAL CIRCULATION WE PERFORMED EXPERIMENTS USING DIFFERENT-SCALE WATER MODELS,A 1/20TH MODEL AND A 1/6TH MODEL. THE TEMPERATURES AND VELOCITIES AT TYPICAL POINTS WERE MEASURED IN TRANSIENT CONDITIONS WITH VARIOUS HEATING RATES AS PARAMETERS. THE MEASURED TEMPERATURES AND VELOCITIESWERE TRANSFORMED TO VELOCITIES WERE TRANSFORMED TO DIMENSIONLESS FORMSFOR COMPARISON AND THE EFFECTS OF THE BO NUMBER AND THE GR NUMBER WEREEXAMINED. IT WAS CLARIFIED THAT THE EFFECTS OF THE GR NUMBER IS NEGLIGIBLY SMALL BUT THE EFFECT OF THE BO NUMBER STILL WAS WITHIN THE EXPERIMENTAL RANGE. THE BO NUMBER OF AN ACTUAL PLANT IS WITHIN THE RANGE OF THIS EXPERIMENT. ACCORDINGLY,THE SIMILITUDE OF THE BO NUMBER IS IMPORTANT IN EXPERIMENTS TO SIMULATE ACTUAL PLANTS.

報告者

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