

  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.



