I've been watching the coverage of Japan and the breach of the nuclear reactors. One thing I noticed is Iodine being passed out on the news footage. Iodine is given so in the case of radioactive iodine exposure, the body will pass the radioactive iodine,and take up the regular iodine. Unfortunately, this only works in the case of radioactive iodine, other radioactive elements will invade the body and cause damage. In Japan, they have detected radioactive cesium in the initial explosions. Interesting enough, radioactive iodine is used in medicine to treat Thyroid defects like hyperthyroid. So taking iodine may only be as useful as hiding under a desk in a nuclear attack.
CDC has a link: http://www.bt.cdc.gov/radiation/ki.asp