Reply #22: You might wanna look at some of that refresher training [View All]

Because there isn't a single form of "radiation". Which is why some of it is more dangerous than others.

From a plant like the ailing one in Japan, the primary dangers are radioactive Iodine and Strontium. Both emit a 'beta particle' when they decay. Another name for a beta particle is a high-energy electron. It can only cause damage if it's inside, or next to a cell in your body. Your skin, since the outer layers are dead, provides a barrier against all but extremely strong sources. So standing next to the reactor would be a very bad idea, but low-level exposure to the outside of your body isn't an issue.

Incorporation is the issue - where your body incorporates the radioactive I or Sr. The radioactive material is inside your body, where it can do damage. Which is where those iodine and calcium tablets come in. If you flood your body with "normal" I and Ca, you'll literally piss away any radioactive I or Sr before they have a chance to do much damage.

Alpha emitters would be even safer, since alpha particles are huge, and easily blocked by skin...or a single sheet of paper. Gamma particles are the nasty stuff, since that penetrates very easily into our bodies.