Abstract The analysis of the flow behavior within a cooling panel of a scaled water-cooled reactor cavity cooling system has been performed supported by high-resolution measurements of the void fraction at the risers’ outlet. The results have shown a stable, symmetric distribution of the flow through the risers during subcooled boiling conditions, characterized by small, slow bubbles with average void fraction lower than 0.3 for all risers. As the temperature increased to saturation, flow distribution appeared strongly asymmetrical and unstable, with peaks of void fraction as high as 0.9. Large, faster bubbles were observed during these peaks, immediately followed by flow of subcooled liquid water. Flow stagnation and inversion has also been observed. The high resolution void fraction results, complemented by the measurements of the coolant flow rate and temperatures, not only have further described the behavior of the system under hypothetical accident conditions, but represent a unique set of data to support the validation of system-level codes, and more advanced computational tools.

中文翻译：

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反应堆腔体冷却系统冷却板中的两相流测量和观察

摘要 对水冷反应堆腔体冷却系统冷却板内流动行为的分析得到了立管出口空隙率的高分辨率测量的支持。结果表明，在过冷沸腾条件下，通过立管的流量具有稳定、对称的分布，其特征是所有立管的平均空隙率均低于 0.3 的小而缓慢的气泡。随着温度升高到饱和，流动分布出现强烈的不对称和不稳定，孔隙率峰值高达 0.9。在这些峰值期间观察到大的、更快的气泡，紧接着是过冷液态水的流动。还观察到流动停滞和反转。高分辨率空隙率结果，