When I first mentioned that I was going to be headed to Japan for Operation Tomodachi, I was flooded with phone calls, emails, and concerned visitors stopping by to remind me that there was apparently a nuclear holocaust in progress and my vacation planning was going poorly. My grandfather came by and told me about how he'd just read in the news about how the USS RONALD REAGAN had just gone through the fallout cloud and seventeen guys on board were dosed with deadly radiation* and all sorts of other horror stories.
At that point I'd feel safe in saying that I had a better understanding of radioactivity than most people. I feel safe in saying that because most people have no understanding of it at all. I've at least had to sit through a few classroom sessions and a tour of a nuclear power plant on my way to getting an engineering degree.
However, since I got here I've still taken it upon myself to learn all sorts of things about radiation, nuclear power, radioactive contamination, and more. Like everyone else I've been hearing reports of radiation levels and contamination and wondering whether the folks exposed were going to die a sudden ugly death riddled with cancer or if they would walk away with something akin to a sunburn. These things are worth knowing.
The first thing to understand is the difference between radiation and contamination. Right now, the bulk of the problem we're looking at in Fukushima is radio-iodine that's been coming from the plant. Radio-iodine is a particulare type of iodine that emits potentially harmful radiation for a few weeks as it decays.
The best analogy I've come across to explain this comes from a brief I read from the 31st MEU. It was designed to explain the problem of radioactive contamination to the infantry grunts getting ready to help with the clean-up efforts on O Shima. It goes about like so:
1. Contamination is pooh.
2. Radiation is stink from the pooh.
3. Large amounts of pooh = very strong stink. The equipment we use measures stink, not pooh.
4. In this case, there's not a lot of pooh. Instead, there's a very thin layer of pooh. Thin enough that there's almost no smell.
5. If you step in it, some gets on your shoes. Then you track pooh all over your floor.
6. If you reach down and touch it, or pick up something that's covered in it, now you have pooh on your hands or your shirt.
7. On your clothes it's unsanitary. On your hands you could rub your eyes. Your eyes don't like pooh. Even a little.
8. Say you touch something you eat. Now you have pooh in you. You body doesn't like that. Even a little. It can cause all sorts of problems.
9. If you want to play in the area where the pooh layer is, remember to cover your feet if you want to walk in it. Cover your hands if you want to pick up or touch things. If it's going to touch your shirt or pants, cover those too. Don't touch your face and you'll be fine.
You've gotta love the Marines.
This analogy leaves out considerations of cumulative exposure over prolonged periods of time, but in the current operating environment they're working in, the worst of the contamination we've seen anywhere can be pretty well eliminated with soap and water.
Now if you've been hearing about radiation levels in the news, you've been hearing about the amount of stink that the radiation sniffers have noticed. These amounts are expressed using all sorts of interesting units like greys, sieverts, microsieverts, and so on. It's been a long time since I took my last exam on this sort of thing, so I've been hopeless in trying to remember what any of them mean.
Fortunately, xkcd.com posted a helpful chart that explains, in reasonably simple terms, just how much radiation is a bad thing while comparing them to the amounts of naturally occurring radiation that everyone in the world is exposed to all the time. Check it out below.
(click for ginormous version)
Hopefully you've found these things as useful as I have.
*There have been a few occasions since this operation started where there've been reports about Navy crews getting contaminated. In every case so far, these have been minor bits of contamination which were simply washed off.