ABSTRACT

Pool scrubbing is one of the promising means for mitigating radioactive aerosol release into the environment in nuclear severe accident scenarios. The influence of operational conditions on its performance is therefore of much interest. This paper focuses on the influence of particle number density found in our experiments. The experiments, conducted for insoluble monodispersed (0.5 µm) particles, indicated a sharp decrease in the decontamination factor (DF) for inlet number densities higher than ~1 × 10¹¹ m⁻³. A model is proposed based on a hypothesis that particle removal becomes inefficient at high number densities because particle condensational growth is limited by the depletion of vapor supersaturation in rising bubbles. The model calculates the magnitude of supersaturation from the bubble mass and energy balances considering the condensational vapor consumption and heat addition by all particles in the bubble, where the rate of condensation on each particle is dependent on supersaturation. The particle size, condensationally growing with time, is then used in the calculation of centrifugal particle removal. It is shown that the model reproduces qualitatively the experimental dependence of DF on particle number density, providing further proof that such dependence is a physical reality deserving attention in the evaluation of pool scrubbing performance.

摘要

池洗涤是在核严重事故情景中减少放射性气溶胶释放到环境中的有前途的手段之一。因此，操作条件对其性能的影响非常重要。本文重点讨论我们实验中发现的粒子数密度的影响。针对不溶性单分散 (0.5 µm) 颗粒进行的实验表明，对于高于 ~1 × 10 ¹¹ m ^{-3 的}入口数密度，去污因子 (DF) 急剧下降. 提出了一个模型，该模型基于以下假设：在高数密度下，颗粒去除效率低下，因为颗粒凝结生长受到上升气泡中蒸汽过饱和度的消耗的限制。该模型根据气泡质量和能量平衡计算过饱和度，考虑到气泡中所有粒子的冷凝蒸汽消耗和热量增加，其中每个粒子上的冷凝速率取决于过饱和度。然后将随时间凝结增长的颗粒尺寸用于计算离心颗粒去除率。结果表明，该模型定性地再现了 DF 对粒子数密度的实验依赖性，