Estimates of Fallout in the Continental U.S. from Nevada Weapons Testing Based on Gummed-film Monitoring Data

Abstract

During periods of weapons testing at the Nevada Test Site (NTS) between 1951 and 1958, the Environmental Measurements Laboratory (EML) monitored daily fallout at about 100 sites in the U.S. using gummed-film collectors. These gummed-film data represent the only comprehensive set of actual measurements of fallout during this period for areas outside the immediate vicinity of the NTS. The measured beta activities originally reported by EML have been reviewed and reevaluated. This reevaluation corrected a number of errors in the original data set and allowed fairly accurate estimates to be made of specific radionuclide depositions from individual NTS shots. Estimates of the geographical and temporal variations in cumulative 137Cs and 131I depositions from all NTS shots through 1957 are presented, as well as estimates of the relative impact of particular shots and test series. The revised gummed-film estimates of total NTS fallout depositions are compared with estimates based on contemporary and historical soil sample analyses. These reevaluated gummed-film fallout deposition estimates are being extensively utilized in a number of ongoing programs to reconstruct the radiation exposure of the U.S. population from Nevada weapons testing.

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

“…Some additional amount would have been cleaned up and disposed of within the NTS, but this additional fraction would have been small compared to the total amount. The estimated 10% of the total fraction is consistent with earlier estimates by Beck et al (1990) and by the NCI (1997) of the total amounts of 137 Cs and 131 I, respectively, estimated to have been deposited within the continental U.S. Beck et al (1990), based upon gummed film data and isopleths for the entire country, had estimated that 21% of the 137 Cs from the tests through Hardtack II had been deposited within the continental U.S.; they further speculated that the total deposition, including that on the NTS itself, would have been 25 to 30% of the total release of 137 Cs. In the course of its study of thyroid doses delivered to the residents of the U.S. from nuclear tests at the NTS, the NCI (1997) estimated the deposition of 131 I in each county of the U.S.; their summary value was that about 25% of the 131 I released was deposited within the U.S.…”

“…3 are also consistent with those drawn by Beck et al (1990) for the entire country. As expected, due to the additional information available for the NTS itself and the Phase I region, the isopleths in Fig.…”

“…Between 1980 and 1985, all of the available data on fallout from the NTS were reanalyzed as part of the ORERP (Beck 1984;Anspaugh et al 1990;Beck et al 1990;Cederwall et al 1990;Church et al 1990;Quinn 1990;Ward and Whicker 1990;Whicker et al 1990;Beck and Anspaugh 1991;Grossman and Thompson 1993;Thompson et al 1994 The strategy adopted for the RIDP combined three methods: Aerial surveys, soil-sample collection and analysis, and field-gamma-ray spectrometry. The aerial surveys, carried out with an array of scintillation detectors mounted on a helicopter, showed overall distribution patterns but were not useful for quantifying individual radionuclides.…”

“…The gummed film collectors were part of a worldwide network operated by the Atomic Energy Commission between 1951 and 1960. Data from the collectors were originally not considered useful for quantifying fallout, but a reevaluation that included a better estimate of the collection efficiency of the film showed that reasonably precise estimates of deposition densities were possible (Beck 1984;Beck et al 1990). …”

¹³⁷Cs Environmental Half-life without Remediation: Impact on Radiation Dose

“…time of arrival of the cloud) that was the culprit in delivering the higher levels of fallout and dose. The total doses in southern Utah from the fallout from all Nevada tests have been estimated to be between 1-30 mSv (BECK 1966, BECK et al 1998, CHURCH et al 1998, ANSPAUGH and CHURCH 1986, LLOYD et al 1990). Most of this dose in Southern Utah was from 131 I and gamma-shine from shortlived radionuclides.…”