caCd. 2 = j =x Ss 7, P i rcti | + ret, | + Rx Actx (3) Act, i=] These mean ranges were determined for the Bravo Crater “standard” sample (using the concentrations in Appendix Table 3); and for those lagoon samples wher @ 23042405 241, and the 238 U decay chain contributors to the sample alpha radioactivity were measured. Using the meen range (4.58 mg/cm”) calculated from equation 3 for the Bravo crater "standard" sediment, conventional self absorption relations (equation 4) were used to predict the values of the counting rate versus samole thickness in the Bravo Crater "standard" sample. (oPMeFe.) + (2) + (FLE.) | rf] | wt | 1-2RT' 00d 4°(2.22) = pCi/g (4) where: R N S sample mg/cm® Nv Eff = counting efficiency = 0.47 range of the alphas (mg/cm ey F.F. = fractionation factor = 0.5452 for lagoon samples or .8870 for the Bravo "standard" These values, along with the observed values are shown in Appendix Figure 2. The agreement of the two curves is very good with the exception of four points wnich occur nearest to the critical thickness range. These deviations may reflect the importance of surface irregularities at these thicknesses. The mean count rate of all the aliquoted samples which had