Abstract The international EU-SGTR and ARTIST projects investigated the transport of fission products in the form of aerosols during SGTR severe accidents. The major finding of the two projects was that there was significant retention of aerosols in the steam generator secondary side, and that the retention was increased by more than an order of magnitude if the secondary side of the steam generator was flooded with water. Furthermore, the experiments with the flooded secondary side showed that the aerosol particle retention was significantly increased due to the presence of submerged structures, i.e., the tube bundle, as compared to an empty pool. The increased aerosol retention was attributed to the interactions of the high velocity gas jet discharged from the tube break with the dense bundle of the steam generator tubes. Under these conditions, the two-phase flow is very complex due to the high gas velocities and complicated geometry of the steam generator secondary side. To determine the effect of the tube bundle on aerosol retention, hydrodynamic characteristics of an empty pool and a flooded steam generator secondary side were measured in a facility equipped with wire-mesh sensors. The facility was equipped with either a tube bundle consisting of 221 steam generator tubes, or with a single tube in the center of the facility. The flow development could be followed by making the measurements at different distances between the gas injection and the measurement point, and using different flow rates. The facility was operated at close to ambient conditions. Void fraction, bubble size distributions, gas phase velocity as well as interfacial area concentration were determined based on the wire-mesh sensor data. In addition, the penetration depth of the initial large gas bubble into the channel was studied for the closest break-sensor distances. The investigations show distinct differences between the flow characteristics in the single tube geometry and in the tube bundle. As compared to the single tube, the flow was more confined in the tube bundle due to the interactions of the flow with the tubes. The interfacial area between the liquid and gas phase is larger with the tube bundle than with the single tube and also the bubble size distributions show distinct differences between the two geometries.

中文翻译：

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SGTR严重事故工况下两相流流体动力学研究

摘要 国际EU-SGTR 和ARTIST 项目调查了SGTR 严重事故期间气溶胶形式的裂变产物的运输。两个项目的主要发现是蒸汽发生器二次侧存在明显的气溶胶滞留，如果蒸汽发生器二次侧充满水，滞留量增加一个数量级以上。此外，与充满水的二次侧的实验表明，与空池相比，由于水下结构（即管束）的存在，气溶胶颗粒保留显着增加。增加的气溶胶滞留归因于从管破裂处排出的​​高速气体射流与蒸汽发生器管的密集束的相互作用。在这些条件下，由于蒸汽发生器二次侧的高气体速度和复杂的几何形状，两相流非常复杂。为了确定管束对气溶胶滞留的影响，在配备有金属丝网传感器的设施中测量了空水池和溢流蒸汽发生器二次侧的流体动力学特性。该设施配备了由 221 根蒸汽发生器管组成的管束，或者在设施中心配备了单根管。可以通过在气体注入和测量点之间的不同距离处进行测量并使用不同的流速来跟踪流动发展。该设施在接近环境条件下运行。空隙率、气泡尺寸分布、基于丝网传感器数据确定气相速度以及界面面积浓度。此外，针对最近的破裂传感器距离，研究了初始大气泡进入通道的渗透深度。研究表明，单管几何形状和管束中的流动特性之间存在明显差异。与单管相比，由于流动与管的相互作用，流动更受管束限制。管束的液相和气相之间的界面面积大于单管，并且气泡尺寸分布显示两种几何形状之间存在明显差异。对于最近的破裂传感器距离，研究了初始大气泡进入通道的渗透深度。研究表明，单管几何形状和管束中的流动特性之间存在明显差异。与单管相比，由于流动与管的相互作用，流动更受管束限制。管束的液相和气相之间的界面面积比单管大，而且气泡尺寸分布显示两种几何形状之间存在明显差异。对于最近的破裂传感器距离，研究了初始大气泡进入通道的渗透深度。研究表明，单管几何形状和管束中的流动特性之间存在明显差异。与单管相比，由于流动与管的相互作用，流动更受管束限制。管束的液相和气相之间的界面面积大于单管，并且气泡尺寸分布显示两种几何形状之间存在明显差异。