solidsurfacealliance.org Blog

June 5th, 2008
Boring stuff, but necessary, these units of radiation. Confusing, math required as well, but knowing the basics is the only way to keep up with the debate. I’ll keep it simple, leave out lots, and later you can fill in the gaps as you learn more about the issues.
First off, three things need to be measured:
1, The amount of radiation emitted. Activity
2. How much was absorbed by your body. Absorbed dose
3. How much damage did it do to your body. Dose equivalent
Some people like to use boxing as an analogy, how many punches were thrown, how many hit your body, and how much damaged did the landed punches cause.
Now it gets a little more complicated.
The rest of the world uses different units than we do in the USA and there are older units still found in some studies found on line.
The US uses Curie (Ci), Rad (r), Rem , and Roentgen (R). Uh oh, I mentioned four and we only had three to talk about. I’ll get to it.
The rest of the world uses Becquerel (Bq), Gray (Gy), and Sievert (Sv).
Curie measures the amount of radiation, same as a Becquerel.
1 Bq = 1 disintegration per second (dps) 1 Ci = 3.7 x 1010 dps 1 Ci = 3.7 x 1010 Bq
Rad measures the absorbed dose, same as Gray.
1 Gray = 100 Rad
Rem measures Dose Equivalent, same as Sieverts.
1 Sv = 100 rems
We will use the US units on this site for the most part, but sometimes the standard units are needed. Use the conversion factors above to convert into US units when needed.
Now what about Roentgen? That is a unit used to describe how much air is ionized by the radiation, which is how a Geiger counter works. So a result posted in Roentgens will pretty much tell you that it was a Geiger counter that measured the radiation.
But wait, some good news! For our discussion, we can figure that Rad, Rem, and Roentgen are roughly the same. Some particles like neutrons or Alpha are different, but for external exposure, we can assume Rad, Rem, and Roentgen are close to the same.
A Rem or a Sievert are very large quantities. We will need something smaller to discuss radiation. Standard math prefixes are used, most common are micro and Milli. A Milli is 1,000th of something. A micro is 1,000,000 of something. So a 1 Milli Rem (1 mR) is 1,000 times larger than 1 micro Rem (1 uR).
Now we have to add something, how long was the exposure? Usually hours or years are the units used, as in 1 mR/hr or 8,760 mR/yr. Remember that R can be thought of as Rem, Rad, or Roentgen.
If you have any questions, just post a comment and I’ll try to help.
Al