ual radiation from fallout will follow approximately the expressions: i = tt? and 2 r= A (1.1) dt = 5], (ty? ~ t, 4) ty Where: Kk = exposure rate at time t I, = exposure rate at unit time t = time r = exposure between times t; andt,, where t = 10 seconds. It is expected that the decay of the residual radiation will vary with device design. For example, the presence of Np”** would tend to decrease the absolute value of the decay exponent for a period of time. 4 YT X EXPOSURE ROENTGENS 3, \ LN \ GAMMA 10" ‘NX X S N Xx ‘\ < __-—FISSION PRODUCTS GAPTURE TO FISSION RATIO #Q5 “oC REFERENCE 8) NN w nin aw \ - ‘\ ~“ io” N _ ‘NX =4 ~~ NC > 10 Ny 3 3 DISTANCE FROM GZ, 10° YARDS ‘ NN ae Figure 1.1 Gamma exposure for 1 kt surface burst. 1.3.3 Absorption in Air. The absorption of unscattered gamma radiation in air is exponential with distance. From a point source of mono-energetic radiation, the variation of intensity with distance is expressed as: hel? Ip ~ (1.2) 47D2 11