Experimental study of volatile iodine retention by pool scrubbing: Influence of operating conditions

In the event of a nuclear power plant accident, iodine is one of the radionuclides of the greatest issue. Present in various chemical forms, the mitigation of outside releases is a crucial aspect of nuclear safety protection measures during a nuclear accident as these airborne iodine releases pose a significant radiological risk to the exposed population in the short term. Pool scrubbing device is one mean of mitigation. Tests were conducted on to study the scrubbing efficiency in a water pool of volatile iodine species: methyl iodide (CH₃I) and molecular iodine (I₂). This allows us to determine a Decontamination Factor (DF) for each gaseous species, characterizing its trapping capability. The influence of various physical and chemical factors on the trapping was investigated, the experimental parameters were the gas flow regime, pool’s pH, and pool’s temperature. The retention of CH₃I by pool scrubbing was unaffected by the flow regime and pool chemical conditions in contrast to I₂. Pool scrubbing appears to be an efficient mean to mitigate I₂ releases for bubbly regime and alkaline conditions whereas for CH₃I, due to its too high volatility, the retention efficiency remains quite low and cannot be considered as an effective mitigation mean.