1989 Fiscal Year Final Research Report Summary
Gas Entrainment Inception from a Free Surface of Fast Breeder Reactor
| Project/Area Number |
63460232
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Nuclear engineering
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| Research Institution | THE UNIVERSITY OF TOKYO |
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Principal Investigator |
MADARAME Haruki The University of Tokyo, Faculty of Engineering, Associate Professor, 工学部, 助教授 (80092336)
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| Project Period (FY) |
1988 – 1989
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| Keywords | Fast Breeder Reactor / bubble / entrainment / bubble Formation / Free Surface / Turbulent Flow Analysis |
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| Research Abstract |
A rapid liquid flow into a tank may impinge on the free surface making it swell partially. The returning flow branches off from the free surface and re-submerges at the border of the swollen surface. When the flow velocity along the swollen surface is high enough, gas bubbles are formed at the border and entrained by the liquid flow. If a significant concentration of gas is entrained by the sodium flow in a plenum of a fast breeder reactor, bursts of gas bubbles may pass through the reactor core, causing a change in reactivity. Gas entrainment must be carefully prevented in fast breeder reactor design. The conditions necessary for gas entrainment in a simple system were examined experimentally, using water and air as working fluids.
The simulated coolant flowed in through a hole on one side of the rectangular test section, and out through many holes in the bottom plate.
The height of the free surface, the width of the section and the inlet hole size were parametrically varied to investigate the scale effect. The effect of surface tension was examined by adding a surface active agent to the water. The results showed that the gas entrainment inception is determined by the width of the test section and the product of the Froude and Weber numbers based on the local velocity at the bubble formation point. A computer code for analyzing the two-dimensional turbulent flow with free surfaces was developed, thus the local velocity and the free surface configuration can be calculated by the code.
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