Nuclear Engineering and Technology Programme, Department of Mechanical Engineering, IIT, Kanpur 208016, India; National Aerosol Facility, IIT, Kanpur 208016, India.
Department of Civil Engineering, IIT, Kanpur 208016, India; Centre for Environmental Science and Engineering, IIT, Kanpur 208016, India.
J Hazard Mater. 2021 Sep 15;418:126356. doi: 10.1016/j.jhazmat.2021.126356. Epub 2021 Jun 9.
Cesium compounds if present in atmosphere, can affect human health as well as the ecosystem due to their highly hazardous nature. Interaction of cesium compounds with abundantly available atmospheric salts can modify the hygroscopic behavior in sub-saturation relative humidity (RH) domain. Any marked modification in growth factor (GF) for the mixed particle state in comparison to the single particles ultimately affects the settling rates and hence the deposition flux. This work studies the hygroscopic behavior of two important cesium bound fission product aerosols (CsI, CsOH) internally mixed with some common atmospheric particles viz. [Formula: see text] and NaNO for a fixed dry particle size of 100 nm. Experimental measurements, performed with Hygroscopic tandem differential mobility analyzer in the range of 20-94% RH, have been compared with the predictions made from Zdanovskii-Stokes-Robinson (ZSR) approach. Apart from the single/pure particle state for the constituents (i.e. mixing ratios 1:0 and 0:1), three other mixing ratios 1:4, 1:1 and 4:1 have been considered. The results show that the GF vs RH pattern for mixed particles is different from that for single CsI and CsOH particles. The intrinsic water uptake behavior for these cesium compounds was found to be perturbed for some of the chosen combinations as well. Deliquescent transition for the mixed particles was observed at lower RH compared to the single electrolytes. Relative differences noticeable for the chosen mixing ratios could be related to the available fractions in the mixed state. Overall, ZSR method was found to be capturing the trend of increasing GFs with increasing RH. Terminal gravitational settling velocities calculated from the measured GFs were also found to be different for single and mixed particles. The relative difference was significant for some combinations and test conditions. Any modification in settling velocity ultimately impacts the deposition flux estimations. Hence neglecting the presence of atmospheric salts affects the accuracy of the source term estimates for a postulated nuclear reactor accident scenario.
铯化合物如果存在于大气中，由于其高度危险的性质，会影响人类健康和生态系统。铯化合物与大量存在的大气盐相互作用会改变亚饱和相对湿度（RH）范围内的吸湿性。与单一颗粒相比，混合颗粒状态下的生长因子（GF）的任何显著变化最终都会影响沉降速率，从而影响沉积通量。这项工作研究了两种重要的铯结合裂变产物气溶胶（CsI、CsOH）与一些常见大气颗粒（即[公式：见文本]和 NaNO）在固定干颗粒尺寸为 100nm 时的吸湿行为。在 20-94%RH 范围内使用吸湿串联差分迁移率分析仪进行的实验测量与 Zdanovskii-Stokes-Robinson（ZSR）方法的预测进行了比较。除了组分的单一/纯颗粒状态（即混合比为 1:0 和 0:1）之外，还考虑了其他三种混合比 1:4、1:1 和 4:1。结果表明，混合颗粒的 GF 与 RH 模式与单一 CsI 和 CsOH 颗粒不同。还发现，对于一些选定的组合，这些铯化合物的固有水分吸收行为也受到了干扰。与单一电解质相比，混合颗粒的溶解转变在较低的 RH 下发生。对于所选混合比，明显的相对差异可能与混合状态下的可用分数有关。总体而言，ZSR 方法被发现能够捕捉到随着 RH 增加而增加 GF 的趋势。从测量的 GF 计算得出的终端重力沉降速度也发现对于单颗粒和混合颗粒是不同的。在某些组合和测试条件下，相对差异显著。沉降速度的任何变化最终都会影响沉积通量的估计。因此，忽略大气盐的存在会影响对假定核反应堆事故情景的源项估计的准确性。
