from previous shots in the area of the detonation (see Section IV.C.2.1.1, Table IV.C.1, and Section V.C.3.2, comment [6]), and participant groups undertook activities in the forward area soon after detonation (Maag et al., 1983; Frank et al., 1981; USMC, 1957).

The locations of all shots at the NTS through Operation PLUMBBOB— excluding shots in Operation RANGER, which did not result in significant fallout on the NTS (Hawthorne, 1979)—are shown in Figures V.C.2 through V.C.6 (see Section V.C.3.2). As discussed in Section V.C.3.2, comment [6], the area near Shot HOOD experienced fallout from several previous shots, and there probably was additional fallout from other shots not mentioned. On the basis of locations of PLUMBBOB shots shown in Figure V.C.6 and fallout patterns reported by Hawthorne (1979), Shot SMOKY, which occurred after Shot HOOD, apparently deposited fallout in the same area. In addition, later safety shots in Operation HARDTACK-II—including OTERO, VESTA, JUNO, and GANYMEDE—deposited fallout in the area of Shot HOOD (Hawthorne, 1979).

Concentrations of radionuclides in surface soil in Area 9, where Shot HOOD occurred, were measured during the 1980s (McArthur and Mead, 1987; McArthur, 1991). Estimated distributions of the photon-emitting radionuclides 241Am, 60Co, 137Cs, and 152Eu in the vicinity of Shot HOOD are shown in Figures E.1 through E.4; additional data on 154,155Eu are not shown. The high radionuclide concentrations to the south and southwest of Shot HOOD presumably are due mainly to fallout from HARDTACK-II safety shots that occurred after Shot HOOD (Hawthorne, 1979). Distributions of 90Sr and plutonium in surface soil were derived from the distributions of 137Cs and 241Am, respectively, and measured 90Sr-to-137Cs and 239,240Pu-to-241Am activity ratios in soil samples obtained from various locations in the area. Distributions of 238Pu also were estimated from measured 238Pu-to-241Am ratios in soil samples.

The information summarized above can be used to estimate concentrations of important radionuclides that were present in the area of Shot HOOD at the time of detonation. On the basis of measured concentrations of longer-lived radionuclides in surface soil after the period of atomic testing shown in Figures E.1 through E.4, measured activity ratios obtained from soil samples (McArthur, 1991), and the ICRP’s current dose coefficients for inhalation of respirable particles (AMAD, 1 μm) given in Table V.C.2 (see Section V.C.3.1), 239,240Pu probably posed the most important inhalation hazard at the time of Shot HOOD, and the presence of 60Co, 90Sr, 137Cs, 152,154,155Eu, 238Pu, and 241Am probably increased potential inhalation doses by less than a factor of 2.1

1  

A more rigorous analysis would need to consider the presence of additional radionuclides with half-lives sufficiently short that they were no longer present in detectable amounts when measurements were made during the middle 1980s. Additional fission products that could be important in aged fallout in the area of Shot HOOD include 89Sr, 95Zr, 106Ru, and 144Ce (see Table V.C.2).



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