APPENDIX V Srief Summary of the Radiological Status of the Bikini Atol. Philip F. Gustafson Fallout Studies Branch Division of Biology and Medicine May 1968 A number of radiological surveys of Bikini Atoll have been made since 1°46. The most recent survey was conducted in April and May 1967. The main effort was devoted to the measurement of ambient radiation levels using several types of detectors. The external radiation field was mapped in con- siderable detail on Bikini and Eneu Islands, and less thoroughly on the remainder of the atoll. The various radionuclides and their concentrations which gave rise to the observed radiation Field were determined from field gamma-ray spectrometry. Representative samples of local plants and animals which might be caten by the returning natives were collected and have been analyzed for radioactivity. The results of the 1967 suvvey provide a basis for making reasonable estimates of the total (external plus internal) radiation exposure which the Bikinians might receive over the coming years, atoll. Background radiation on the atoll is due almost cxclusively to cosmic radiation, radioclements detonations, and there are only trace amounts in the area. the Except 207 OO. Co, and of the naturally occurring in the immediate vicinity of nuclear composition of the residual gamma-ray radioactivity was similar throughout the atoll, nae if they return to the 10% to place; Eneu was 2d Sb. the consisting of about 70% 137¢5, , Variations least contaminated, A dose gradient existed across Bikini, and highest values . — in intensity were observed with followed by Bikini lowest Island itself. levels on the in the heavily overgrown interior. from place beach areas,