58 THEORETICAL CALCULATIONS OF THE GAMMA RADIATION SPECTRUM, ETC. TRE SHORTER-TERM BIOLOGICAL HAZARDS OF A FALLOUT FIELD target paramoters. Unfortunately, however, fallout gamma sources are not constant nor even easily predictable. For different weapons types the very nature of the radioactive materials available for fallout may vary. For example, some devices may produce significantly large vields of induced activities in addition to fission products. and so on. However, even for a given weapon type, soil and nieterological conditions will vastly alter Hitt) 0.39 O08 «Ot Og 0.20 O28 ENERGY (Mev) 0.20 Froure 19.--Plane isotropic source, differential energy spectrum, 3 feed above the plane, Ey==0.855 Mev. feot above a plane contaminated with a source emitting monoenergetic photons of 0.255 Mov. Despite the proximity to the “ground,” much of the radiation reaching the detector position originates at considerable distances and is significantly degraded by a long path through air before reaching the detector. The abrupt peak and discontinuity seen on this chart represent the maximum energy loss achievable in a single Compton interaction: namely, the case where the secondary photon is emitted at 180° to the path of the primary photon. There are in Figure 20 the integral dose and energy spectra corresponding to the differential dose spectrum of Figure 19. Similer spectra are calculable for other source cnergies, of course, and from these solutions interpolation curves can be drawnup. In order to calculate crudely dose spectra from fallout once the source onergies are’ known, an interpolation curve such as that of Figure 21 can be used. Yts use and interpretation are the same as for the case of interpo- lation curves for pointisotropic gamma sources, as discussed earlier. 0.10 With a sample source spectrum similar to the one applied before to the point source case, but now modified to fit the plane source orfallout case, the integral dose spectrum of Figure 22 was generated. For the ehergetic sample F(t,B) » Integral Bueray D(t,Z) « Integral pose source used, there is relatively little degraded radiation received by the gamma detector. The next step would logically appear to be O18 analogous to the procedure applied to the initial gamma case: that is, normalization of fallout source spectra to actual weapon or o20 O25 ENERGY (Mev) Fraurn 20,-—Plone isotropic source, integral energy and dose spectra, 3 feet above the plane, Ey=0.255 Mev, 448029 O-—58-——--5 So- called “clean’* weapons will producerelatively few fission products and may produce comparateely siguificant induced activities from soil— 0.85 Q 59