tact that would be valid for all cases, one might assume the worst case where the material remains in place until its activity has decayed to an insignificant level. Dose rates could then be approximated, to yield a given infinity dose. by: D= 5At where: D = infinity dose A = dose rate at time "t", If the above discussion is accepted, then the remaining question is to set the infinity dose. Here, we must be clear that whereas the measurements taken by the monitors, and the data upon which action will be decided will be gamma dose rate readings, the point of principal concern is the beta dose delivered to the basal layer of the epidermis (assumed as 7 milligrams per square centimeter)... The ratio of emission of beta to gamma is a function of time after detonation and follows no simple relationship. Further, this ratio at any given time after deton- — ation has not been firmiy established. ing data; _\ | One report* suggests the follow- . AfterDetonation Beta/Gamma 72 hours 168 hours 157/1 156/1 These data were obtained from a cloud sample, rather than actual fallout Materia., and were a measure of surface dose on a plaque using a "dosi- — meter type beta-ray surface ionization chamber." The method of collection suggests the possibility that the thickness of material on the plaques may be less than that to be expected from the amount of fallout that would be of concern when estimating probabilities of beta burns. This would result in a different angular distribution of the betas influencing the beta dose rate in the direction of a higher value for the plaques. *WI=26. Scientafic Director's Report, Annex 6.5. Survey-meter Data’, SECRET. - 16 fr v7 "Interpretation of