It should be emphasized that this analysis presumes that the radioactive 

 contents of the package are suddenly released to the environment in a form 

 V^ich is subject to diffusion processes. The assumption of a semi infinite 

 medium ( infinite depth ) was made in this case ; the effect of finite depth will 

 be felt yfhen the material has diffused significantly to the actual surface, which 

 occurs only after C at the source has dropped by a factor of about 1000. 

 Thus Fig. 3 should be adequate up to about 10 hours even if the depth is of the 

 order of 30 meters . 



It can be shown that for sufficiently large distances from the finite box 

 source (r » a) , Eq. (6) reduces approximately to 



3_ =f_iL_\ expf-JLL], (12) 



^oi l^^v V 4Kty 



In view of Eq. (11) this formula is the same as the point source formula (4) if 

 the source strength is taken as 2 M, ( to account for the boundary effect which 

 is represented by an image source of strength M. ). 



If an upper boundary is imposed at z = D , through which no flux can occur 

 then we must add a succession of image sources along the z axis at intervals 

 of 2D above and below the actual source hi order to achieve the correct 

 boundary conditions at both top and bottom . The resulting relation for C^ for 

 X , y > D and sufficiently large t is 



Ci 



= ± _^ exp [- -^VtJ^ I (13) 



3 

 which corresponds to a uniform line source of strength 4a C . /D along the 



