105 process was evaluated for the most abundant alpha-emitting radionuclides, 23942405 The assumption made following this evaluation was that the other alpha-emitting radionuclides were similarly distributed between the whole and aliquoted samples. A second possibility for the different summed concentra- tions is that the mean range of the alpha particles calculated for use in the concentration calculation was incorrect. Because this is a difficult parameter to estimte, it might seem to be the most likely parameter to have an appreciable error. However, the fit of the theoretical self-absorption curve calcu- lated by using this range to the experimental self-sbsorption curve (Appendix Fig. 2) is in excellent agreement. It is obvious that several other alpha-emitting radionuclides other than those measured individually in this sample are present in the Bikini sediments. These radionuctides are both those which are naturally occurring and those produced during the nuclear testing. The most abundant naturally occurring radionuclides (under natural conditions) not measured in this work were 2305, and the members of the 235 U and 232 Th decay chains. Although the concentra- tions of 2307, and 235 U in this sample were not measured, their probable abundances can be estimated. The activity concentration of 230 Th should not exceed the measured 234 U concentration (2.45 pCi/g) which would be a conservative estimate. The sum total concentrations of all the naturally occurring 2354 chain alpha emitting radionuclides cannot exceed 1 pCi/g, assuming that th e 235 U concentration is 1/21.8 of the measured 234) concentration and that all the 235 U daughter radionuclides were in radioactive equilibrium with 235 U. The concentrations of 2327p measured in both recent and old Fniwetok corals is very Tow (Thurber et al., op. cit.) so that it misht be expected that the Presence of 228, in these sediments vould set an upper limit to the contribution of alpha concentrations from this decay chain. Moore and Krishnaswany