報告書番号

383013

タイトル（和文）

温度成層化現象に及ぼすレイノルズ数およびリチャードソン数の影響

タイトル（英文）

EFFECTS OF REYNOLDS NUMBER AND RICHARDSON NUMBER OF THERMAL STRATIFICATION IN A HOT PLENUM

概要 （図表や脚注は「報告書全文」に掲載しております）

タンク型高速増殖炉における原子炉トリップ時に発生する炉内温度成層化現象は炉壁や内部機器に大きな熱応力を及ぼす。ここでは単純なホットプレナム模型を用いた熱過渡実験を実施し温度成層化現象に及ぼすレイノルズ数Ｒｅとリャードソン数Ｒｉの影響について検討を加えた。その結果，Ｒｅ数が１００００以上の場合，成層界面の上昇速度や界面での温度勾配はＲｅ数に依存しないこと，また界面上昇速度はＲｉ数の－１／２乗に比例し，界面の温度勾配はＲｉ数が増加するにつれ急峻になることが示された。さらにＲｅ数が１００００以上かつＲｉ数が１～５の範囲では大規模な界面の波動現象が生じ，その周期はＲｉ数の－１／２乗に比例して変化することが明らかにされた。以上の結果は，実機を模擬した縮小模型実験結果と定性的に一致し，実機の熱流動現象を評価する上で役立つものと考えられる。

概要 （英文）

THERMAL TRANSIENT WATER TESTS WERE PERFORMEDTO EXAMINE THE CHARACTERISTICS OF THE THERMAL STRATIFICATION IN A HOT PLENUM OF POOL-TYPE FBRS.THESE TESTS WERE DIVIDED INTO TWO SERIES.IN THE FIRST SERIES THE REYNOLDS NUMBER(RE) EFFECTS ON THE THERMAL STRATIFICATION WERE EXAMINED AND IN THE SECOND SERIES THOSE OF RICHARDSON NUMBER(RI) WERE EXAMINED.THE VALUES OF RE AND RI OF CORE OUTLET FLOW WERE AS FOLLOWS, FIRST SERIES: RE 6000-27000,RI=4 SECOND SERIES: RE ABOVE 10000,RI=0.5-16.IN THESE TESTS A HOT PLENUM MODEL WITH THE SIMPLIFIED CONFIGURATIONS WAS USED.THE DIAMETER AND THE WATER DEPTH OF THIS MODEL WERE 80CM AND 50CM RESPECTIVELY. IN THE FIRST SERIES OF TESTS,IT WAS FOUND THAT IN THE RE RANGE BEYOND 10000,THE RISING SPEED OF THE INTERFACE INCREASED AND THE TEMPERATURE GRADIENT AT THE INTERFACE DECREASED AS THE VALUE OF RE INCREASED.ON THE OTHER HAND,IN THE RE RANGE ABOVE 10000,THE RISING SPEED AND THE TEMPERATURE GRADIENT WERE FOUND TO BE INDEPENDENT OFRE. THE EXPERIMENTAL RESULTS OF THE SECOND SERIES INDICATED THAT THE RISING SPEED OF THE INTERFACE VARIED PROPORTIONALLY WITH RE TO THE MINUSHALF POWER.IT WAS ALSO FOUND THAT THE TEMPERATURE GRADIENT AT THE INTERFACE INCREASED WITH INCREASING THE VALUE OF RI. IN THE RE RANGE ABOVE 10000,LARGE SCALE INTERNAL WAVES,CALLED INTERNAL STANDING WAVES,WERE OBSERVED IN THE FIRST SERIES OF TESTS.THE SECOND SERIES OF TESTS REVEALEDTHAT THE INTERNAL STANDING WAVES WERE GENERATED IN A RESTRICTED RANGE OF RI,1-5.THEIR NONDIMENSIONAL WAVE PERIOD WAS FOUND TO VARY PROPORTIONALLY WITH RI TO THE MINUS HALF POWER. FROM THESE RESULTS,IT IS CONCLUDED THAT RI OF CORE OUTLET FLOW PLAYS AN IMPORTANT ROLE IN THE BEHAVIOR OF THE THERMAL STRATIFICATION IN HOT PLENUM IF THE VALUE OF RE IS LARGE ENOUGH.

報告者

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