APPENDIX V Brief Summary of the Radiological Status of the Bikini Atoll Philip F. Gustafson Fallout Studies Branch Division of Biology and Medicin May 1968 A number of radiological surveys of Bikini Atoll have been made since 1946. The most recent survey was conducted in April and May 1967. The main cf£ort 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 survey 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. if they return to the Background radiation on the atoll is due almost exclusively to cosmic radiation, and there are only trace amounts of the naturally occurring radioclements in the area. Except in the immediate vicinity of nuclear detonations, the composition of the residual gamma-ray radioactivity was similar throughout the atoll, consisting of about 70% 137 cg, 20% 0066, and 10% 12385, to pJace; Eneu was the Variations in intensity were observed from place least contaminated, followed by Bilcini Island itselr. A dose gradient existed across Bikini, with lowest levels on the beach areas, and highest values in the heavily overgrown interior. LO1349bo6