42 THE SHORTER-TERM BIOLOGICAL HAZARDS OF A FALLOUT FIELD 1.0 THEORETICAL CALCULATIONS OF THE GAMMA RADIATION SPECTRUM, BTC. INITIAL BOMGAMMA RADIATIONS Tn order (0 calculate a solution for an actual weapon source, however, the emission spectra of tho previously mentioned fission product gammaa and nitrogen capture gammas must be known, and the absolute abundance of cach o8 of these soureca must be weighted according to the pertinent. weapon parameters in order to determine air doses and spectra as a function of distance. These considerations are treated in detail in the classified literature and will not be developed here. In substance, however, appropriate fission productand nitrogen capture too a0 60 80 OG 40 Ptr, x10" 30 O82 ¥(r,B) = Integral Roergy D(r,E) « Integral Dose ° os So Lo 2.0 2.6 ENERGY (Mev) Fraunn 2.--Point isotropic source, integral energy and dose spectra at 1,000 yards, Eo 2 Men, attenuated photons only. In other words, then, the dose build-up factor can be determinedtheoretically by this method. Thus the build-up factor for a 10 Mev source 3,000 yards awayin air would be one divided by one minus 0.66, or 2.27. : By using such interpolation curves and com- bining solutions for several energies, one can determine spectra from polyenergetic gamma sources, thus beginning to approach the case of an actual bomb gammasource. As an example, Figure 7 presents an integral dose spectrum 1,000 yards away from an arbitrary source made up of 40 percent 1 Mev photons, 15 percent 2 Mev, 6.7 percent 3 Mev, and 2.5 percent 4 Mev photons. 43 ENERGY (Mev) Frovure3. ~~Point isotropic source, differential energy spectrum, at 3,000 yards, Ho=2 Mev. 448029 O—-58—4