Abstract Wet scrubber-based filtered containment venting systems (FCVSs) are commonly deployed at nuclear power plants, owing to the high degree of aerosol, iodine, and organic iodine retention that is possible through the pool scrubbing action that takes place during their operation. However, after a FCVS has been operating during a severe accident, the pool water will become extremely contaminated with previously-captured radionuclides, and the bubbling action of gases passing through the pool, could result in the re-entrainment of contaminated liquid droplets into the gas stream. This would produce a secondary source term during the late phases of an accident. As such, a set of experiments have been conducted in order to evaluate the aerosol re-entrainment rates and size distribution from a system prototypical of a pool-type FCVS. Entrainment rates were measured by tracking the carry-over of a NaCl tracer into a set of liquid traps, while the size of the re-entrained droplets was measured with a phase Doppler anemometer. The experiment employed a prototypical venturi nozzle and gas injection conditions to examine the influence of gas flow rate, liquid level, and pool water temperature. Entrainment factors between 5 × 10−5 and 1 × 10−3 were measured, and the water droplet count median diameters were between 3 and 13 µm, and fairly wide particle size distributions, with mass mean diameters were on the order of 40–140 µm. These experimental results help the assessment of the potential magnitude of the late phase source term hazards posed by the fission products retained in pool-type FCVS (secondary release), and the potential loading on the secondary dry filter stage (metal fiber filters) employed in FCVSs after the primary pool scrubbing stage. The secondary metal fiber filters should have a high efficiency in capturing water droplets produced through this mechanism, given the droplet’s relatively large size.

中文翻译：

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湿式洗涤器过滤式安全壳通风系统再夹带的实验评估

摘要 基于湿式洗涤器的过滤式安全壳通风系统 (FCVS) 通常部署在核电厂中，因为在其运行期间发生的水池洗涤作用可能会保留高度的气溶胶、碘和有机碘。然而，在严重事故中运行 FCVS 后，池水将被先前捕获的放射性核素严重污染，通过池的气体的鼓泡作用可能导致受污染的液滴重新夹带进入池中。气流。这将在事故后期产生次要源项。因此，已经进行了一组实验以评估来自池型 FCVS 系统原型的气溶胶再夹带率和尺寸分布。夹带率是通过跟踪 NaCl 示踪剂进入一组液体陷阱来测量的，而重新夹带的液滴的大小是用相位多普勒风速计测量的。实验采用原型文丘里喷嘴和注气条件来检查气体流速、液位和池水温度的影响。测量了 5 × 10−5 和 1 × 10−3 之间的夹带因子，水滴计数中值直径在 3 到 13 µm 之间，粒径分布相当宽，质量平均直径约为 40-140微米。这些实验结果有助于评估池型 FCVS（二次释放）中保留的裂变产物造成的晚期源项危害的潜在程度，以及在初级池洗涤阶段之后用于 FCVS 的二级干式过滤器阶段（金属纤维过滤器）的潜在负载。考虑到水滴的尺寸相对较大，二级金属纤维过滤器在捕获通过这种机制产生的水滴方面应该具有高效率。