Summary statement of findings related to the distribution, characteristics, and biological availability of fallout debris originating from testing programs at the Nevada Test Site

Abstract

Summary statements are given of significant findings related to the distribution characteristics, and biological availability of fall-out debris originating from testing programs at the Nevada Test Site during the past decade. The delineation of fall-out patterns has been accomplished by the use of aenial and ground monitoring surveys. Only about 25% of the total amount of fission products produced by tower-supported detonations were deposited within distances corresponding to fall-out time of H + 12 hr; a much smaller quantity was deposited by halloon-supported detonations. Fall-out particles less than 44 (For in diameter are presumed to be of the greatest biological significance. About 30% of the fall-out radioactivity from tower-supported detonations was contained in the 0 to 44 (For particles as compared to almost 70% for balloon-supported detonations. Fall-out debris from halloon- supported detonations was also much more water and acid soluble than was the debris from towel-supported detonations. The those calculated by the T/sup -1.//sup 2/ relationship. Fall- out radioactivity is apparently confined to the first 2 in. of the soil surface unless the surface has been mechanically disturbed. Most of the fall-out debris that was redistributed by various environmental factors after original deposition consisted of particles < 44 (For in diameter; the particles in this size range also represented the predominant contamination on plant foliage. Sr/ sup 90/ levels in surface soil ranged from 31.9 to 142 mc/sq. mile in virgin areas near known fall-out pattern midlines and from 7.5 to 22.7 mc/sq. mile in agricultural areas that in some cases did not coincide with fall-out pattern midlines. The accumulation of radioiodine by native animals was observed to be a function of distance from GZ. Ba/sup 140/, Y/sup 91/, Sr/sup 89/, and Sr/sup 90/ were major bone contaminants. Post-series sampling of native aminals indicated that the accumulation of Sr/sup 89/ was also a function of distance from the point of detonation; however, the Sr/sup 90/ accumulation by animals correlated poorly with the strontium unit levels in soils. The strontium unit levels increased in milk immediately following contamition of the farm with fall-out debris and then decreased with time as well as the amount of strontium associated with the cattle's diet. Observations during the past decade indicate that less than 10% of the total strontium produced from nuclear detonations at NTS has been deposited with 200 miles from the point of detonation. (auth)« less