Page 932 - Radiation Safety

Equatio D m = 0.55 C (  f E ) rad.hr at 1 meter
-1
1

n where:

D m : Dose rate (rad/hr) at 1 meter
1
C : Activity in Ci
HVL  2 n   o E : Energy of gamma (MeV)
f : Fraction of gamma of that energy produced

n per disintegration

TVL  10 n  o

 n

n= # of HVL or TVL

I = Dose rate after shielding
n

. 0 693

HVL 
u

. 2 303

TVL 
u

Ao : original activity (at t = 0)
-t
At : activity after time t A = A e =
 : decay constant t o
t : time internal
T 1/2 : half-time of the radioisotope A e -0.693t/T 1/2
o