15 



point, so far neglected ; for isotopes of relatively small half lives (say of the 



f 

 order of a year or less) , the material deposited 14 years earlier will have 



decayed by containment to a very small level. By ignoring the natmral decay, it 

 is obvious that our considerations of the activity in the medium is far over- 

 estimated. 



One final question -v^^ich mi^t be considered is the following : Suppose a 

 steady state has been established, with a 14 year accumulation of activity in the 

 disposal area ; then what activity concentrations could be developed in the water 

 around the source area , if all of the packages are suddenly destroyed by an 

 unforseen catastrophe ? To answer this we may refer to Eq. (17) and use 



^oi - — f ^''^ 



Thus for r > D 



If we take 



4a' 



47 

 C^. = . 2M, (27) 



mi 



4Dr 



and 



then 



D = 30 meters 



5, M. = 14 X 100 curies 



^ 137 

 for Cs 



r = 1 km 



3 



C = 5 . 5 u. c/ m 

 mi 



= .0055 H-c/kg " (28) 



