Yes I misstated what Iodine could prevent. Unintentional my omission was that iodine will only reduce the amount of radioactive iodine absorbed by the thyroid, and prevent thyroid cancer at a later date.
As far as radiation sickness, avoiding contact with the dust as much as possible will help prevent absorbtion. Keep inside in a well sealed area. After a few days, the dust will settle. If possible, bathe in non contaminated water. Although remember that water resources may be in short supply, and may be better served by saving for drinking.
Yup - well said.