| Budget Amount *help |
¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 1986: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1985: ¥2,300,000 (Direct Cost: ¥2,300,000)
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| Research Abstract |
In postulated breaks in cold legs for LWR's or the advanced thermal reactor (ATR), downward two-phase flow may arise in the reactor core. In this case, ECC water is designed to be injected from its top, to flow downward in the core; its flow rate is limited by the CCFL - counter current flow limit. Thus, this project aims to investigate into the characteristics of downward flow especially focusing on its flow instabilities; some might be caused by the CCFL, resulting in the dryout of heating rods.
In this study, the follwing two types of experiments are carried out. Firstly, the experimental apparatus is made of the two heater channels, each consists of a 1-st riser, a downcomer and a 2-nd riser. From this experiment, three types of instabilities are observed: a 2-nd-riser-governed dynamic instability, an excursion type instability which leads to a blockage in one channel, and another one type. The second experiments are carried out with four heated downcomers, and two instability types are observed. For low flow rates, steam void goes upward against falling liquid flow, being accumulated at the top where the dryout is initiated. For high flow rates, the flooding causes the dryout at the bottom. Analyses are performed for these phenomena, which results show good agreement with the experimental data.
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