BZebhed Fallout at Elmer Sacondary fallout was detected by beta laboratory background counters at Elmer at about 24 hr after Shot 1; 11 to 16 hr and 45 to 100 hr after Shot 23; 4 to 6 hr after Shot 4; and 12 to 14 hr after Shot 6. The activities found were generally not over 50 times back~ ground and were not high enough to constitute a real hazard to personnele 305 GAMMA ACTIVITY The Rad Safe Gamma ground readings (Appendix C) measured shortly after each sot and which were apparently representative ground readings were corrected back to one hour after each, shot, the time by which the peak of significant activity had been reached. This time was estimated from the time of arrival results obtained from the intermittent fallout collector. The correction is made by the expression ' 1.2 a, ® a4 1 where 2 (3.20) ty A2 is the observed activity at time, t> A, is the activity calculated at time, t; The exponem 1.2 is an approximation. In the absence of the actual exponent associated with the gamma decay its use lies within the accuracy associated with the actual ground readings obtained and the relatively short period of time involved in the extrapolation. The survey readings resulting from contamination from previous shots were subtracted as background in determining the level of activity associated with a subsequent detonation. These dose rates are shown in Figse 318 to 3.22. Segments of isodose rate lines have been drawn as solid lines where island dose rate readings, together with wind vector data, make mch approximations reasonable. Where no data was available, the isodose rate lines are shown as dashed lines. Infinite gamma dosages, based on Rad Safe ground readings, were algo calculateds they indicate the hazard associated with permanent occupation of an area with the same degree of contamination. These values are underlined in Figse 3018 to 3.22. 3.6 BETA ACTIVITY CONCENTRATIONS The total beta activity per unit weight or volume associated with a sample composed of mixed nuclides is defined as the activity concentration. It refers to the plus the low energy gana activity detected by the beta counting equipment. As used here, the activity concentration can be thougnt of as being similar to what is usually referred to as the "specific activity” of a particular isotope ina sample. The activity concentration of the liquid phase collected in the 8~oz jars was deternined by counting an aliquot portion of the filtrate after it had been evaporated to dryness. 66 The activity con-