This information is taken from an article by Dr. Kathy S. Grant in the August 1987 copy of Journal of Civil Defense. Table 1 International System of Units (SI) and conventional units.(for 80 col. Physical SI UNIT Conventional Relationship Quantity unit 10 Activity becquerel(Bq) curie (Ci) 1 Ci = 37 X 10 Bq -1 1 Ci = 37 Gbq(gigabequerels) (s )(s to the negative one power) -4 Exposure coulomb/kilogram roentgen(R) 1 R = 2.58 X 10 C/kg (gamma & (C/kg) 1 R = 258 uC/kg(microC/kg) X-ray only) (no special name) Absorbed gray (Gy) rad 1 rad = 0.01 Gy Dose (J/kg) 1 rad = 10 mGy(milliGray) Dose sievert (Sv) rem 1 rem = 0.01 Sv Equivalent (J/kg) 1 rem = 10 mSv(milliSieverts) (you can see why Petr Beckmann compares using Bequerels to measure radiation is like using angstroms to measure shoelace length) Table 2. Quality factor (Q) for different kinds of radiation Q Type of Radiation 1 X-ray, gamma, and electrons(beta) 2-3 Thermal Neutrons 10 Fast neutrons and protons 20 Alpha particles Table 3 SI prefixes (sysop's shorthand 10/4 = ten to the fourth power, 10/-7 = ten to the negative seventh power etc.) Factor Prefix Symbol 10/18 exa E 10/15 peta P 10/12 tera T 10/9 giga G 10/6 mega M 10/3 kilo k 10/-3 milli m 10/-6 micro u 10/-9 nano n 10/-12 pico p 10/-15 femto f 10/-18 atto a (for those of you lacking lower case everything below mega M symbol is in lower case, the micro is a backwards lower case u) (surprise your friends, use these in your day to day speech, "I don't give a femtodamn about it!") Activity A curie was defined as the activity of radon in equilibrium with one gram of radium. This value was later standarized at 3.7 X 10/10 per second. A bequerel is one disintegration per second. By convention 1 Ci = 3.7 X 10/10 Bq. (note that no attempt is made to compenstate for the fact that various elements when disintigrating release more than one particle or form of radiation) Exposure The roentgen measures the amount of ionization that gamma rays or xrays produce in air. In SI 1 R = 2.58 X 10/-4 coulombs per kilogram. The coulomb is not an SI base unit; it is defined as an ampere-second) Absorbed dose The rad is defined as 100 ergs absorbed per gram of material (0.01 J/kg) The gray is defined as 1 joule (J) absorbed per kilogram of material. Therefore, 100 rad = 1 Gray. Dose equivalent Equal amounts of radiation can do differing amounts of biological damage. This is mostly due to the volume of the absorbtion, example alpha radiation dumps all of its energy in to just the point of contact and gamma sources spread the energy throughout an much large volume of tissue. To adjust this difference they have come up with a quality factor. The REM is Roentgen Effect in Man. The SI dose equivalent (H) = D X Q X N, where D=Dose in grays, Q=quality factor, and N=a further modifying factor that the author didn't explain.