PRELIMINARY EXTERNAL-DOSE ESTIMATES FOR FUTURE BISINI ATOLL INHABITANTS Abstract with the objective of evaluating the potential radiation doses that may be received “vo the retutning Bikinians, a survey was -onducted during June 1975 cf the residual radio~ ctivity in the terrestrial environment on Bikini and Eneu [Islands of Bikini Atoll. The survey included measuring environmental gamma-ray exposure rates for use in evaluating “he external gamma doses, and collecting numerous soil, lens water, and vegetation samples ror use in assessing the internal doses via pertinent food chains. This report describes the gamma-ray exposure rate measurements and their use in conjunction with population statistics and expected life styles for evaluating the potential external gamma-ray doses associated with various options for housing locations on Bikini and Eneu Islands. (The evaluation of the internal dose contribution via food chains will be published in subsequent reports.) The results of the survey reveal that the external exposure rates on Bikini Island ire nigniy variaole. Values near ine shores are generally of the order of 10-20 JUaAYur, wnile those within the interior average about 40 uR/hr with a range of roughly 30-100 uR/hr. Eneu Island, however, is characterized by more or less uniformly distributed gamma radiation levels of less than 10 uR/hr over the entire island. For the external dose determination a set of most likely living patterns was chosen. ihese were based upon the various options for housing locations along the lagoon road and within the interior portions of Bikini Island as well as along the lagoon side of Eneu Island. As expected, living on Eneu Island results in the lowest doses: “he first year and 2.7 rem during 30 years. 0.12 rem during The highest values, 0.28 rem during the first ,ear and 5.7 rem over 30 years, may potentially be received by inhabitants living within the interior of Bikini Island. Other options under consideration produce intermediate values. Introduction A radiological survey of Bikini and Eneu Islands of the Bikini Atoll was conducted during June 1975 to assess the potential radiation doses that may be received by the returning Bikinians. the Pacific. Bikini Atoll was one of the U.S. nuclear weapons testing sites in It is situated in the northern part of Micronesia in the Central Pacific Ocean about 3600 km southwest of Honolulu. The atoll consists of a number of small islands on an elliptical coral reef surrounding a lagoon with major and minor axes having dimensions of 35 and 27 km, respectively. The islands are shown in Fig. 1. ~l- The total