ooane0 chim ret) = Kk, Ge (t) x (15) bh Equation 15 suggests that, for the stated assumptions, vary inversely with distance. - wv M(t) shoulda For small particles where the falling velocity is preportional to the square of the diemeter, the masé con- tour ratio for those particles is given by 7 , vee) = 2el ye | kx k G in which k, is a constant. (6) 3 For these assumed conditions, Me(t) decreases with the square root of the distance. For the second case, the average specific activity is given by (a,/m,) = k, in which k), is‘a constant. (17) For this case where the specific activity is independent of the particle diameter, M2(t)is independent of the dis- tance and is given by W(t) = — kK, G, (18) Although Eq. 18 does not contain a distance term and in that sense is not a point function, the region of its applicability is, of course, restricted to the area within which the particles with a constant speci- fic activity fall. DOE /NW In addition to the distance, x, Eqs. 15 and 16 suggest that the value of M°(t) depends on the wind velocity and the height from which the particles fall. The latter depends on weapon yield. If the bottom of the clouds is used as a reference point with respect to the measure ~ - .