BATTELLE Dr. Rudolf J. Engelmann NORTHWEST -2- was conducted on December 8, Site. March 12, 1971 1968 at the Nevada Test Several days after the event, W-181 was the predominant radionuclide detected and it served as a unique tracer. The half-life of suspended radioactive particulates was observed to be 38 days. Resuspension factors were between 6 x 1075 and 1077 m-l. The half- life and resuspension factors are in general agreement with the SNAP-27 paper. Unanswered questions still remain which we suggest should be answered. Admittedly the half-life is of the resuspension factor as being equal to the airborne concentration divided by the ground concentration. Typically, the airborne concentration has been measured from 3 to 6 feet above the ground surface. Such a definition may be satisfactory if we assume that the resuspension factor is to be applied to inhalation at the test site, For the immediate inhalation problem, field experiments are stated (p. 6, UCRL-72534) to suggest that an inverse relationship exists between the resuspension factor and the level of deposited activity. Since this is true, we really do not know the physics of resuspension. That report suggests that "the mass deposition at high activity areas is sufficiently high to significantly lower the amount of material available for resuspension, or that air levels in low ground activity areas mainly represent suspended material that originated in high ground activity areas far removed from the point of measurement." At first inspection, we tend to agree that the inhalation hazard is due to upstream resuspension. The physics of resuspension from upstream conditions to the local inhalation hazard must be determined. “SET : ant ro They oe A serious question exists concerning the definition mESY could be resuspended before the 30 day half-life occurred. te ete eh aes ct, lives for longer time periods? Half-lives for resuspension are needed for time periods beyond the initial half-life and for time periods for which soil movement is great. If soil movement were great, all activity ON TPR der mee og es ErNeah Ya initially between 30-40 days, but what are the half- a