Resolving Nevada Test Site and global fallout plutonium in attic dust and soils using 137Cs/239+240Pu activity ratios

A simple equation using only Cs-137/Pu239+240 activity ratios was developed and evaluated as a means of resolving the plutonium in attic dust and soil from Nevada and Utah that came from Nevada Test Site fallout from that which came from global fallout. Applied to an historical data set of Cs-137 and Pu239+240 activity concentrations in soils from Nevada and Utah, the activity ratio method gives results similar to the traditional Pu-240/Pu-239 isotope mass ratio method, Considering the difficulty and expense of determining the Pu-240/Pu-239 atom ratios, this activity ratio method is simpler, faster, and less costly, and may be useful for detecting and/or monitoring plutonium contamination in soils. Applied to samples of attic dust and soil collected from throughout southern Nevada and Utah during 1996 and 1997, it was found that all sites surveyed showed the presence of Nevada Test Site plutonium, Over 90% of the plutonium found in the samples from Beatty, Tonopah, and Queen City Summit, Nevada, can be attributed to the Nevada Test Site.