Radiation Dose in Autoradiography 129 



Minimum Dose for Short-lived Elements 



Inserting the expression for the minimum concentration 

 (equation 6) in the general equation for the dose (equation 

 5) we obtain: — 



T 



a-d 5X1U ^^^^^^ e 



k(T)f(T)e-^^ dr reps (12) 



o 



Using the same assumptions which led to equations (7), 

 (8), (9) and (10), equation (12) can be simplified. 



T 



A ^At 



k(T)f(T)e-^'' dr reps (13) 



o 



f(t) 



where B=6lE^Co. 



Bs== — „ for stripping film (14a) 



11 



Bx=36 ^ for X-ray film (14b) 



For work with long-lived isotopes: — 



Bs=800 ^ (15a) 



B'x=38 5|! (15b) 



The following solutions of equation (13) were computed 

 under the assumption that k is independent of time. It 

 should be noted that for computations, the values for the time 

 should be in days, and the value for A based on time of decay 

 in days. 



(a) Linear increase or decrease of concentration 



f(T)=aa-|-br 



ISOTOPES 10 



