explosives, and are not due to fission reactions. Because of the toxicity of the scattered material, however, both from the standpoint of its chemical and radioactive properties, and because its long half-lives (228pu, 87.4 yrs; 73%Pu, 24,390 yrs; 7*°pu, 6,600 yrs), it is essential to prevent Pu from reaching man on both short- and long-term bases. “Long-term'' infers that methods essential to prevent Pu from reaching man should be effective from 10's of years to time periods bordering the geological time scale. As to which preventative methods are chosen to achieve this end, the final decision must be predicated on both efficiency and cost, as well as such environmental parameters as disruption or destruction of the biota in affected areas and the potential recovery of the areas. Plutonium's characteristics make it particularly important to exclude the element from man's food chain, or drinking water, but most importantly to prevent inhalation of plutonium particulates by man. From time to time, a number of theoretical methods have been proposed for preventing plutonium in contaminated NTS areas from reaching man or his domestic animals, or animals which contribute directly or indirectly to his food supply. Among these proposed methods are the following: 1. Scraping and removal of the soil surface from contaminated areas. This could be accomplished at relatively large expense, although the methods would likely not be efficient in areas which have very shallow soils with intermittent rock outcrops. Removed materials would be stored, presumably, in locations not subject to wind, water, or human or animal exposures. stored areas themselves would, of necessity, become exclusion areas with problems paralleling those of the present with me exception as to localization. 166 The