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PRELIMINARY EXTERNAL-DOSE ESTIMATES
FOR FUTURE BIKINI ATOLL INHABITANTS
Abstract’
With the objective of evaluating the potential radiation doses that may be received
by the returning Bikinians, a survey was conducted during June 1975 of the residual radioactivity 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
the external gamma doses, and collecting numerous soil, lens water, and vegetation samples
for 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
are highly variable.

Values near the shores are generally of the order of 10-20 uR/hr,

while 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 theentire island.

.

.

For the external dose determination a set of most likely living patterns was chosen.
These 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:

0.12 rem during

the first year and 2.7 rem during 30 years. The highest values, 0.28 rem during the first |
year 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.

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Introduction

A radiological survey of Bikini and Enel 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 oneof 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

_isiands 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. . The total

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