SMALL BOY SHOT FALLOUT RESEARCH PROGRAM 51 The value of K, has been computed for uniform depositions of unfractionated fission products on ideal smooth planes. However, the calculated values of K, from observed values of I, over real terrain for a given value of A, or A,, are lower than those computed for the ideal plane because of attenuation of the gamma-ray intensity by both small- and large-scale roughness of real terrain, nonidealized re- sponses of radiac instruments used in measuring the intensity, and decreased contributions from the morevolatile fission-product radionuclides whose relative concentrations in the fallout are decreased (i.e., the radioactive composition is altered or fractionated). The values of I,, relative to those for the fission products, are increased by :ae production of induced radionuclides (usually through neutron capture) in both weapon components and nearby environmental mate- rials. The representation of Ky), including consideration of the four factors discussed in this paragraph, is given by Ky = Da(r,,k,, + r,k,) where D= q (3) instrument response factor radiation source geometry terrain attenuation factor for the assumed detector— ky = computed value of I,/A; for 3 ft above an ideal plane uniformly contaminated with unfractionated fission products rr, ~ gross fractionation number and is equal to the ratio of I, for the fractionated mixture of radionuclides to the I, for the unfractionated mixture k,;= computed value of the I,/A; contributions from induced radionuclides for the same detector—source geometry as for Kfp r.= gross fractionation number for the induced radionuclides and is related to k; in the same waythat r,, is related to k,, If it is accepted that the radionuclide composition varies with the size of the fallout particles, the major factors in Eq. 3 that are dependent on particle diameter are r;, and r,. In moreprecise treatments, D and q also depend on the radionuclide composition because both of these parameters are functions of gamma-ray energy, which, in turn, depends on the relative abundance of the radionuclides in the fallout. The value of the intensity—area integral for a fallout pattern usually is determined by integration of the standard intensity contours from the highest intensity to a selected low-valued contour. The frac- tions of the radionuclides deposited outside the lowest contour are not included in the pattern summations. Also, the quantities that are buried