* { Apawea® . ) “-APFFNDIXV."TOENCLOSURE2 Bricf£ Summary of the Radivivgical Status of the Bikini Atoll t A CONF 32 dw 38 only D TO BE UNCLASSIFIED AUTHORITY: DOE/SA-20 BY BRo—SCHED? , DATE: B- 2, 611900 Philip F. Gustafson Fallout Studies Branch Division of Biology and Medicine G-l6-Fut . 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 “ulin eziort was devoted to the measurement of ambient radiation levels using ‘severai types of detectors. The external radiation field was mapped in con- »iderabic detail on Bikini and Eneu Islands, and less thoroughly on the cemainaer of the atoll. The various radionuclides and their ‘concentrations which cave rise to the observed radiation field were determined from field gamma-ray spectrometry. Representative samples of local plants and énimals waach might be eaten 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, if they return to the aio.i. Background radiation on the atoll is, due almost exclusivelyto cosmic radiation, and there are only trace amounts of the naturally occurring racioelements in the area. Except in the immediate vicinity of nuclear aetonations, the composition of the residual gamma-ray radioactivity was c.milar throughout the atoll, consisting of about 70% 137¢s, zi. 6000, and 10% 1254, . Variations in intensity were observed from place to place; Eneu was the least contaminated, followed by Bikini Island itself. A dose gradient existed across Bikini, with lowest levels on the beach are ait highest values in the heavily overgrown interior. : : , . fet: m4 442 eG ON