Distribution and Characterization of Plutonium in Soils from Nevada Test Site

Abstract

AbstractThree surface soil samples, contaminated with plutonium by high explosive detonations of subcritical atomic devices at the Nevada Test Site (NTS), were analyzed for total plutonium content, plutonium distribution in different particle sizes, and leachability by HNO3. Total plutonium averaged about 2,640 disintegrations per minute (dpm) per gram of soil. The highest concentration of plutonium in two samples taken from the same area was in the very fine sand (125‐53 µm) fraction (38 and 47%); the third sample from another test area contained the highest concentration in the coarse silt (53‐20 µm) fraction (47%).Leaching with 8M HNO3 revealed that the extracted plutonium was related to the amount of plutonium associated with the finer sizes of soil particles. The highest extraction of 91% was associated with the sample containing 99% of the plutonium in particles < 125 µm; the lowest extraction (65%) with the lowest amount (55%) in the same size fractions. Density gradient separation of a silt and a clay fraction revealed that the plutonium in the silt size was associated with particles whose density was > 2.8 g/cm3; in the clay size the plutonium was associated with particles < 2.2 g/cm3.