Study of the stability of CsI and iodine oxides (IOx) aerosols and trapping efficiency of small aerosols on sand bed and metallic filters under irradiation.

The decomposition of deposited CsI and iodine oxides (IOx) aerosols deposited on sand bed and on a metallic filter has been pursued under irradiation at 120 °C. On the sand, it was found that CsI aerosols are decomposed by the irradiation and the temperature effect into an inorganic specie assumed to be molecular iodine. The temperature effect might be due to surface effects of the sand grains as CsI aerosols are usually stable at this temperature. IOx aerosols are expected to be well retained by the sand filter (DF > 100) as long as the sand height is high enough (>60 cm). IOx are also decomposed by the temperature and irradiation. The humidity is also expected to have a significant influence on their decomposition. On the metallic filter, despite both species are expected to be significantly decomposed, very few gaseous iodine release from the filter was observed. The gaseous iodine species produced by the aerosols decomposition is assumed to be quickly adsorbed on the steel wires even if a slow desorption is also expected. • Thermal and radiolytic decomposition of CsI and IOx aerosols deposited on sand and metallic filter was studied and quantified. • Decontamination factors (DF > 100) were determined for small aerosols like IOx (MMAD ≈ 0.16 μm) deposited on a sand filter whose thickness is over 60 cm. • On the sand filter, it is observed a significant CsI and IOx aerosols radiolytic decomposition leading to a release of gaseous inorganic iodine. A thermal effect is also observed and is assumed to occur at the surface of the sand grains surface. • On the metallic filter, CsI and IOx aerosols are expected to be significantly decomposed. but there is no significant release of gaseous iodine because of the large surface developed by the steel wires on which iodine is expected to be adsorbed. [ABSTRACT FROM AUTHOR]