TABLE 3-2. THE CONVERSION FACTOR (s*/ p) / Np IN @Ci/g)/eps FOR 241Am AS A FUNCTION OF DETECTOR HEIGHT, AIR DENSITY, SOIL DENSITY AND DEPTH DISTRIBUTION Detector Height, h (em) Depth Distribution,@ (em7!) Air Density, Pa Soil Density, Ps (¢/em? ) @/em®) 2.0 1.5 1.0 800 0.33 1.30 8.33 9.10 10.61 800 800 800 800 800 800 800 450 450 450 450 450 450 450 450 450 100 100 100 100 100 100 100 100 100 0.33 0.10 0.10 0.10 0.05 0.05 0.05 0.33 0.33 0.33 0.10 0.10 0.10 0.05 0.05 0.05 0.33 0.33 0.33 0.10 0.10 0.10 0.05 0.05 0.05 1.00 1.30 1.15 1.00 1.30 1.15 1.00 1.36 1.15 1.00 1.30 1.15 1.00 1.30 1.15 1.00 1.30 1.15 i.00 1.30 1.15 1.00 1.30 1.15 1.00 7,89 9.17 8.94 8.7] 9.35 9.11 8.88 7.45 7.39 7.29 8.22 8.11 8.00 8.38 8.26 8.16 6.67 6.67 6.66 7.36 7.35 7.35 7.50 7.90 7.49 8.63 9.49 9.24 9.01 9,52 9.28 9.04 8.14 8.03 7.92 8.50 8.39 8.27 8.53 8.42 8.31] 7.29 7.28 7.27 7.61 7.6) 7.60 7.63 7.63 7.63 10.06 9.60 9.39 9.1] 9.86 9.60 9.36 9.49 9.36 9.23 8.60 8.48 8.37 8.84 8.71 8.60 8.49 8.48 8.47 7.70 7.70 7.69 7.91 7.91 7.90 800 0.33 1.15 8.10 8.85 10.33 The mass attenuation coefficient for Enewetak soil was based on chemical analysis of 124 soil samples obtained from 9 islands during December 1979. These samples were analyzed for organic content as well as elemental composition. Results of the analysis showed that the primary component of Enewetak soil is calcium carbonate. A number of trace elements were also identified. The most significant trace element was magnesium, which contributed approximately 1-2 percent by weight. Although the organic content varied from 0.5 percent to 25 percent by weight, most samples were in the range of 1 percent to 8 percent, with an average of approximately 4 percent for all samples. The in situ mass attenuation coefficient for each sample was obtained from a weighted average of the water, organic and appropriate elemental mass attenuation coefficients. The water content, by weight, for each sample was based on the in situ soil moisture measured with the nuclear density/moisture gauge just prior to collecting the sample. (All samples were dried prior to the ehemical analysis.) The mass attenuation coefficient for organic material was estimated by using the value derived for cellulose. Based on these 124 soil samples, an average value of 0.333 + 0.012 em*/g was obtained for the in situ Enewetak soil mass attenuation coefficient. The average value for the dry, organic-free component was 0.365 em2/g compared to 0.37 em2/p for pure caleium carbonate. (Complete details and results for the soil density and mass attenuation coefficient determination are given in Tech Note 22.) Table 3-3 shows the effect on the 414m conversion factor due to variations (at the 1 and 2¢ level) in the soil density and the soil mass attenuation coefficient. For a fixed mass attenuation coefficient of 0.333 em4/g, a +2o variation in the soil density leads to approximately a +2 percent change in the conversion factor. For a fixed soil density of 1.5 g/em’, a +20 variation in the mass 93