Distribution, characteristics, and biotic availability of fallout, operation plumbbob. BNWL-481.

Abstract

Abstract : This report includes the significant findings of CETO (Civil Effects Test Operation) Program 37, related to the distribution, characteristics, and biological availability of fallout debris originating from the Plumbbob Test Series (1957) at the Nevada Test Site. The use of aerial radiometric survey was adapted to routine radiation surveys and greatly increased the detail, accuracy and distance of fallout pattern delineation. Isodose rate and time-of-arrival contour maps are presented for seven tower mounted and four balloon mounted shots along with the predominant particle size fraction on several arcs along each fallout pattern. Particles less than 44 microns in diameter contained about 30 percent of the fallout radioactivity from tower mounted detonations as compared to about 70 percent from balloon mounted detonations within distances at which fallout arrived by H + 12 hours. Balloon mounted detonations produced fallout debris of higher water and acid solubility than did tower mounted detonations. In the environment, fallout radioactivity was apparently confined to the upper 2 inches of soil unless the soil was mechanically distributed. The majority of the fallout debris which was redistributed by environmental factors on the soil surface after original deposition consisted of less than 44 micron diameter particles; this size particle also represented the predominant contamination on forage plants. Studies clearly indicated that accumulation of radionuclides by mammals cannot be assessed only on the basis of dose rate measurements of the gamma radiation field.