47 contamination problem was detected.° Because a large spectrum of artificially produced alpha emitting radionuclides were present in the Bikini samples, it was decided that particular attention should be focused on possible interferences. To evaluate the extent te which interferences might occur, all long-lived alpha emitting uranium series and transprotactinium radionuclides were listed by their decay energies. A similar table for those isotopes of plutonium, uranium and polonium of interest in this study was made and is shown in Table 7. From the alpha spectra of plutonium, uranium’and polonium samples (Figs. 7, 8 and 9) resulting from this work, it was found that a fairly constant 0.2 MeV energy range (#15 times the peak FWHM resolution) was covered by the typical alpha particle peak detected. Hence, all of the alpha emitting isotopes listed with a sig- nificant proportion of their alpha particle decay energies within the 0.2 MeV limits of the decay energy of the isotopes in Table 7 were considered as being possible interferences. A list of these radioisotopes is shown in Table 8. The absence or removal of most of these radionuclides from the final samples is discussed below. In the plutonium and uranium procedures, radium is removed along with the calcium in the chemical separation process. Isotopes of radon which might Decontamina- tion factors of greater than 1000 are reported by Butler (op. cit.) for the removal of Am, Th, and Np from the final uranium samples, and similarly high RT arere Ae interfere are short-lived and, being gases, present no problems. a. One plutonium reagent blank had a net alpha count o background in an 800-minute counting period in the alpha spectrum. 9.8 counts above Pu region of the Because no other blanks showed such high values, this samples was assumed to have been singly contaminated and no correction was applied to the data as a whole. b. The uranium concentrations of the surface sediment samples shown in Table 13 were calculated from spectra with poor counting statistics, unlike that shown in Figure 8.