In order to clarify the cesium iodide (CsI) transport behavior with a focus on the mechanisms of gaseous iodine formation in the reactor coolant system of light water reactor (LWR) under a severe accident condition, a reproductive experiment of CsI transport behavior was conducted using a facility equipped with a thermal gradient tube. Various analyses on deposits and airborne materials during transportation could elucidate two mechanisms for the gaseous iodine formation. One was the gaseous phase chemical reaction in Cs-I-O-H system at relatively high-temperature region, which led to gaseous iodine transport to the lower temperature region without any further changes in gas species due to the kinetics limitation effects. The other one was the chemical reactions related to condensed phase of CsI, namely those of CsI deposits on walls with surface of stainless steel to form Cs₂CrO₄ compound and CsI aerosol particles with steam, which were newly found in this study.

为了阐明碘化铯（CsI）的运输行为，重点是在严重事故情况下轻水反应堆（LWR）的反应堆冷却剂系统中气态碘的形成机理，我们进行了使用CsI运输行为的生殖实验装有热梯度管的设备。运输过程中对沉积物和气载物质的各种分析可以阐明形成气态碘的两种机理。一种是在相对高温区域的Cs-IOH系统中进行气相化学反应，由于动力学限制作用，导致碘气向较低温度区域的迁移而气体种类没有任何进一步变化。另一个是与CsI凝聚相有关的化学反应，在这项研究中新发现了₂ CrO ₄化合物和带有蒸汽的CsI气溶胶颗粒。