Radiation Exposures in Utah from Nevada Nuclear Tests

Abstract

The exposure of the population of Utah to external gamma-radiation from the fallout from nuclear weapons tests carried out between 1951 and 1958 at the Nevada Test Site has been reconstructed from recent measurements of residual cesium-137 and plutonium in soil. Although the highest exposures were found in the extreme southwest part of Utah, as expected, the residents of the populous northern valleys around Provo, Salt Lake City, and Ogden received a higher mean dose and a significantly greater population dose (person-rads) than did the residents of most counties closer to the test site. However, population doses from external exposure throughout Utah were far too low to result in any statistically observable health effects.

Heavy element radionuclides (Pu, Np, U) and {sup 137}Cs in soils collected from the Idaho National Engineering and Environmental Laboratory and other sites in Idaho, Montana, and Wyoming

“…Assuming that integrated global fallout is characterized by 24"Pu/239pu atom ratios of 0.180, and that this same ratio for NTS fallout at the sampling sites shown is -0.0400, the calculated percentage of WS fallout 239+29?u in the offsite soils sampled is shown in Table 8. The 240pu/239u atom ratio measured in Fontenelle, WY soil in 1993 is -20 percent lower than the same ratio measured by Beck and Anspaugh (1991) in soils at Kemmerer, WY in 1982/1983). The mean and standard deviation of the 24~u/239pu atom ratio observed for all locations sampled west of Yellowstone, WY (Table 6) is 0.159 f 0.012, a value close to that for Idaho Falls, ID (0.166) reported by Beck and Anspaugh (1991).…”

Technical Basis of Dose Reconstruction

“…This dose-reconstruction study for the NTS became known as the Off-Site Radiation Exposure Review Project (ORERP). The historical estimates of external exposure reported by Dunning (1959) were essentially correct (Beck and Krey 1983;Anspaugh and Church 1986;Anspaugh et al 1990;Henderson and Smale 1992;Haskell et al 1994). …”

“…Sophisticated measurements ('37Cs deposition density, 239+240Pu deposition density, and the ratio of 240P~-to-UgP~) of soil samples collected from Utah were also very useful in defining the deposition in Utah that had come from the NTS, even though the majority of '37Cs and Pu had come from global fallout (Beck and Krey 1983). These same techniques were used more broadly in a multi-state area to define the contamination from the NTS (McArthur and Miller 1989), and the results became one of the primary inputs for the County Data Base (Beck and Anspaugh 1991).…”

Inventory and distribution of residual 137cs on and near the Nevada Test Site

“…As dose estimation for the Phase I region was proceeding, Beck and Krey (1983) reported that residents of the Salt Lake City area of Utah had received a greater population dose of radiation than had residents of most counties closer to the NTS. Consequently, the ORERP's advisors recommended that an attempt be made to estimate doses outside the limited region covered by fallout monitors.…”

“…Additional data on 137 Cs deposition were provided by soil samples collected in Utah and western Colorado in 1979 (Beck and Krey 1983) and throughout the rest of the Phase II region in 1982and 1983(McArthur and Miller 1989 Pu is critical in distinguishing the two sources of fallout). The relationships that make this calculation possible are given in Beck and Krey (1983).…”