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.