Ip = Where: 0.3549 - C Lh, 4) K/h (1.1) C = curies per cubic meter Lfh, 6) = a polynomial, dependent on the altitude of the aircraft, h; and half angle, 6 which subtends the diameter at the surface contarnination. The canima rays from the fissicn products are assumed to have an effective gamund energy of 0.5 Mev when 1 to 6 days old (Reference 5). This reference states quantitatively that gamma curies and Lzta curies are nearly equivalent in this period. Estimates based on this assumption indicate that contamination with a beta activity of 4.43 x 10°(dis/min)/liter at the surface shuuld produce a 1 mr/hr gamma flux at 3 feet from the surface, when the diameter of the contamination is large enough to appear infinite (@ = 90 deg). Figure 1.1 Coordinate system of gamma radiation from a water volume. Fallout of 0.404 megacurie per naut mi? deposited in the sea, uniformly mixed to a depth of 60 meters (Reference 3 and Section 3.4.2), would produce a 1 mr/hr gammafield at 3 feet above the surface. The gamma dose rate at any altitude f,, related to the 3-foot value is expressed by the ratio of the polynomials L(h, 90 deg). The altitude absorption 1/f, is plotted in Figure 1.2. 1.3.2 Fallout Contamination of a Land Surface. When fallout is deposited on land, the con- taminated area appears as a large plane source. At any point in the radiation field, the gamma intensity will include contribution from a circle whose radius is determined by the absorption of the gamma photons in air. The dose rate (I,) above such a plane is given by the following equa- tion (Appendix A, Equation A.15). Ip = 3.4427 Cy J(h, 8) x R/hr Where: C J(h, @) curies per square meter a polynomial similar in construction to that in Section 1.3.1. With the same assumptions as for the water case (Eo = 0.5 Mev and the ratio of beta and gamma curies equal to 1), 2.1 x 10"(dis/min)/ft? of beta activity will result in a 1 mr/hr gamma field at 3 feet from the surface, when the source diameter is proportional to @=90 deg. 13 A