ee eeetc 306 TRANSURANIUM ELEMENTS IN SAMPLES COLLECTED NEAR BIKINI ATOLL Table 2. Analytical reauits for plutonium and “4! Am in “Bikini Ash” and munne sediment sumples™ 2¥4On,, _ Sample “Bikini Ash” 73105 TALOR 71109 TRIS zie wa Am (diafmia/gram} 2594 17f 0142005 ANP LURK] LTD LID LTD <0.038 LTD 1.68 002 LTD M1 gy /BPe Mop, 12.92 U.S <0 2 S72 0.42 21s 0.22 <0. 2 Chemical yeh (%) Po Ant Osu 2 as arza 3422 Mpa) 21:3 Gi, ts0,07 IK: | O54+ 0.07 -- 2722 Wes? are Zit? Izetl "The annlyse: were carried out in February, 1974. tdis/minfmig. 73109 are one-to-two orders of magnitude higher than those quoted above. The ??'?"pu detected in sample 73105 is the same level as that of worldwide fallout. It is notable that MMO was not detected in sample 73113. It may be caused by the water depth of the sampling site, since this sample was collected from the deepest site among the four samples, along with the effects of the winds and current at the time of the nuclear testing. Recently, Nevisse and Schell reported You and “Am contents in sediments collected tn Bikint Atoll lagoon (Ne75). They determined the “Am contents by gamma-ray spectrometry. According to thetr data, the contents of plutontum) and americium in 3I samples, including two samples collected outside the atoll, varied from 0.9 to 270 dis/min/g for 2+24 1) and from 0.7 to [70 dis/min/g for “Am, respectively.The ratio ofAmp???’ Pu varied from 0.2 to 0.8, und the average value was 0.53. Compured with those values, the results of marine sediments in this study have reasanable values. Since “Am is a daughter nuclide of *'Pu it seemed interesting to calculate the “Pu content ino the “Bikini Ash’ sample by assuming the “'Am originally present in the bomb was negligible. By considering the growth of “Am from “'Pu in the sample during the 20 yr, the content of 7Pu in the “Bikint Ash’ ts estimated to have the valuc of 666+ 49 dis/minfmg just after the time of detonation. The half-life values of 14.9 yr for 4 "Pu and 458 yr for “Aimare used in these estimates. The ratio of “'Puf??**°’Pu was calculated to be 2643 at the time of nuclear testing. According to the data reported by Dramondef af. (D160), the ratio tn the “Mike” debris is 2743, almost the same as the we i. ot a£ | Pull eta tne CF present value, For sediment samples, the above-mentioned calculations may. not be Were valid becuuse the sediments contaminated with various debris from many other explosion tests carmed out since 1946. It is important from the environmental point of view that the growth of “Am from “'Pu should be taken into account to evaluate the future radioactive contamination of the environment with long life alpha-emutting radtonuclides. CONCLUSIONS By using mination our new technique radiochemical with ‘Gd and deter- **Pu tracers, the americium and plutonium contents in the so-called “Bikini Ash” sample were accurately determined together with the contents of these nuclides in several marine sediment samples collected near Bikint Atoll, This new technique may be applied to the environmental americium determination in the future, and this information on the environmental contamination with transuraniuim elements in this region may be useful for the estimation of focal environmental radioac- tivity due to alpha-emitting radionuclides. The ratio of “Pull? pu for the “Bikini Ash” sample at time zero was calculated to be 26+ 3, and was almost the same with that in the “Mike” thermonuclear debris. REFERENCES Di60) Diamond H., Fields P. R., Stevens C. S., Studier M. H., Fried S. M., Inghram M. G., Hess Db. C., Pyle G. L., Mech J. F.. Manning W. R.., Ghiorso A., Thompson S. G., Higgins G. H., Seaborg G. T., Browne C. 1., Smith H. 1. and Spence R. W., 1960, “Heavy isotope abundances in ‘Mike’ thermonuclear device”, Phys, Rev. 119, 2000. I1s69 Ishimort T. and Akatsu E., 1969, ‘'Preparalion of pun J Nucl. Sci. Technol. 6, 480. JA54 The Japan Society of Analytical Chemistry,