Contamination – This is what happens when you get radioactive material on you, or anywhere it’s not supposes to be. It sits there giving off radiation that can then harm you. It’s why you see all those folks wearing the full body cloth suits that look like the belong in a hospital or electronics plants. The suit doesn’t stop radiation at all (well, it will stop some kinds, but we don’t need to worry about that right now). It keeps all the radioactive material on the outside of you where the suit can be thrown away. Well, it’ll be bagged and stored as radioactive waste, not just thrown in the can.
Exposure – The amount of radiation that has penetrated an object. This is a measurement of the amount of energy the radiation deposits per unit mass of a material.
Dose – A measurement that approximates how much damage a given exposure of radiation will cause to biological tissue. Different forms of radiation can deposit the same amount of energy into a person, but will cause different amounts of damage.
Sievert – The SI unit for measuring radiation dose. One Sievert, abbreviated Sv, is a lot of radiation, enough to cause radiation sickness. Five Sv can cause up to 50% of people who get that dose to die. A milliSievert is 1/1000th of a Sv, and a microSievert is 1/1,000,000th of a Sv. Dose is cumulative, it adds up over time. For example, if you work in an area with radiation levels of 50 milliSv per hour for 10 hours, wou will have a total acute (short-term) dose of 500 mSv, or 0.5Sv. At Fukushima last I heard they are allowing the workers to get up to 250mSv, up from the normal limit of 100mSv. For perspective, a chest x-ray is about 500 microSv, or 0.5mSv.
Ok, that’s it for now. As always, any questions, ask away.