Harold L. Beck,* André Bouville,” Brian E. Moroz,” and Steven L. Simon’
Bravo, a 15-Mt test conducted on | March (local time)
1954, on Bikini Atoll, which, as a result of an unexpected

Abstract—Deposition densities (Bq m~’) ofall important dosecontributing radionuclides occurring in nuclear weaponstesting fallout from tests conducted at Bikini and Enewetak Atolls
(1946-1958) have been estimated on a test-specific basis for 32
atolls and separate reef islands of the Marshall Islands. A
complete review of various historical and contemporary data,
as well as meteorological analysis, was used to make judgments
regarding which tests deposited fallout in the Marshall Islands
and to estimate fallout deposition density. Our analysis suggested that only 20 of the 66 nuclear tests conducted in or near
the Marshall Islands resulted in substantial fallout deposition
on any of the 23 inhabited atolls. This analysis was confirmed

wind shear condition, resulted in heavy fallout on atolls
east of the site and high radiation doses to the populations
of those atolls. Numerous studies have been conducted to
monitor the islands and people, to develop land remediation strategies, and to assess contemporary and possible
future doses that might be received by inhabitants of
certain atolls in the Marshall Islands. Particular emphasis
has been given to the northern Marshall Islands. Many of
these studies were chronicled in a July 1997 special

by the fact that the sum of our estimates of *’Cs deposition

edition of Health Physics.
However, while there have been numerous measure-

from these 20 tests at each atoll is in good agreement with the

total *’Cs deposited as estimated from contemporary soil

sample analyses. The monitoring data and meteorological
analyses were used to quantitatively estimate the deposition
density of 63 activation and fission products for each nuclear

ments made over the decades of radioactivity in soil
collected from many ofthe atolls (particularly the northern atolls and primarily for '*’Cs), no assessment of the
deposition of all of the many radionuclides contributing
to radiation exposure from each test has ever been made
for all of the atolls of the Marshall Islands.
Someof the difficulties in estimating deposition of
the many fallout nuclides at the more than 30 atolls and
separate reef islands has been the absence of measurement data of nuclides other than '°’Cs, lack of a reliable
model for predicting the relative deposition of deposited

test, plus the cumulative deposition of *’*™°Pu at each atoll.

Estimates of the degree of fractionation of fallout from each
test at each atoll, as well as of the fallout transit times from the
test sites to the atolls were used in this analysis. The estimates
of radionuclide deposition density, fractionation, and transit
times reported here are the most complete available anywhere
and are suitable for estimations of both external and internal
dose to representative persons as described in companion
Health Phys. 99(2):124-142; 2010

Key words: '’Cs; fallout; Marshall Islands; nuclear weapons

nuclides for both thermonuclear (TN) and nonthermonuclear (non-TN)tests, and absence of good data


on time of transit for fallout from each test to reach the
atolls from the test sites. There has also been little
information regarding the effects of weathering that

From 1946 through 1958, 66 nuclear weaponstests were
conducted in or near the Marshall Islands, including 23 at
Bikini Islands, 42 at Enewetak, and one at a nearby
open-ocean site (DNA 1979; Simon 1997; Simon and

reduced residual radioactivity, particularly soil '°’Cs

levels, more quickly than would be expected by radioactive decay alone.
In this work, all available historical and contemporary measurement data were collected and reviewed,
including data not previously published in the open
literature. An analysis of these measurements along with
model calculations of relative nuclide activity and estimated fractionation, supplemented by meteorological
modeling, have allowed us to make deposition estimates
of all important fallout radionuclides at all atolls from

Robison 1997). Of special significance was the test
* New York, NY 10014 (retired from the U.S. DOE); * Division

of Cancer Epidemiology and Genetics, National Cancer Institute,

National Institutes of Health, Bethesda, MD 20892.
For correspondence contact: Steven L. Simon, National Cancer
Institute, National Institutes of Health, 6120 Executive Blvd., Bethesda, MD 20892, or email at

(Manuscript accepted 11 August 2009)

Copyright © 2010 Health Physics Society

DOI: 10.1097/HP.0b013e3 18 lbbbfbd

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