74
Planning and Programming
RADIOLOGICAL CLEANUP OF ENEWETAK ATOLL
Task Group were Mr. Tommy F. McCraw (AEC Operational Safety), Drs.
W. Nervik and D. Wilson (LLL), and Mr. W. Schroebel (AEC/ Division of
Biomedical and Environmental Research). The Group was assisted by
average exposure rate was defined for each island. When an average rate
was neededfor a group ofislands, it was obtained by weighting individual
island rates according to the area of eachisland in the group. The exposure
rates were converted to absorbed dose based on assumed duration of
seven consultants. All members and consultants workedeither directly for
the AEC or for an AEC laboratory, and most had been associated with
AEC efforts at Bikini Atoll. Liaison representatives of DNA, EPA, and
DOI attended the Task Group meetings.
The AEC Task Group’s findings were compiled in a ‘‘Report by the
AEC Task Group on Recommendations for Cleanup and Rehabilitation of
Enewetak Atoll,’ which was circulated in draft form for comment in
February 1974 and, after revisions, again in April 1974. There was lively
debate, even among the AECstaff, over aspects of the report. Typical
points at issue were: the appropriate contamination threshold for removal
exposure.
Inhalation dose estimates were determined using the InternationalCommission on Radiological Protection (ICRP) lung model. Intakes to
this model were derived from concentrations of plutonium in soil and an
assumed air-mass loading. (Average concentrations for plutonium in soil
of islands/group of islands were used.) This method was considered
preferable to using thesurvey air sample data, which were representative
only of a very short period of time. Had actual air sample data been used,
inhalation dose estimates would have been several orders of magnitude
lower than reported.
Ingestion dose estimates were based on an assumeddiet (including local
marine andterrestrial food and imported food) and measured or derived
of soil from Runit and Boken, the scientific or technical basis for making a
judgment that plutonium levels in the soil on Runit and Boken were high
enough to justify removal of large amounts of soil; and the limited (3
weeks versus an annual program) air sampling data which indicated that
airborne plutonium levels at Runit were quite low, comparable to some
concentrations of radionuclides in components of the diet. Significant
radionuclides for ingestion dose were determined to be cesium-I37 and
strontium-90. A concentration for these nuclides was determined for the
average fish ofthe atoll, for use in estimating doses via the marine food
pathway. The concentration of the significant radionuclides in terrestrial
levels in the United States.56
Dr. William Ogle, an eminent scientist long associated with the nuclear
test program, was consulted by DNA on the Task Group Report. He
questioned the recommendation that the dri-Enewetak be kept off Enjebi
foods was estimated primarily by correlation between concentrations of
radionuclides in soil and in indicator plants or animals.
The survey report included estimates of annual dose rate ‘and
until subsequent AEC measurements and analysis indicated that they
could return to that island. His concern was based on the belief that the
U.S. would not be in control indefinitely. He recommended that cleanup
actions be taken which would allow the dri-Enewetak free use of the atol!
in the future. Regarding Runit, he felt there was every reason to suspect
that the problem was caused by small particles of plutonium. He
accumulated dose. over extended periods of time for the various living
patterns. The effect on possible dose due to cleanup modifications, e.g.,
covering contaminated soil with clean soil, plowing soil to mix
contaminated surface layers with cleaner subsurface layers, was assessed.
The report ranked dose pathways in the following order of decreasing
dose: ingestion of terrestrial food, external gamma exposure, ingestion of
questioned the need for the dri-Enewetak to stay off Runit.5’ He realized
that the AEC recommendations assumed there was a genuine hazard, but
he felt that the information available did not fully support that assumption.
He felt that Runit should be cleaned as well as possible and turned over to
marine food: and inhalation of contaminated air. The most significant
contribution to dose via the terrestrial food chain was determined to be
strontium-90 in pandanus, breadfruit, and coconut.*°
The Enewetak Radiological Survey provided a data base and general
concepts for radiological cleanup. Considerable effort was still required,
however, to evaluate and adapt the data for actual cleanup operations.
the people.>8
.
DNA believed that the recommended cleanup standards (in terms of
residual radiation) were too low (that is, too conservative), that cleanup to
these levels was not necessary, and that the funds likely to be made
available for cleanup would not permit reducing residual radiation to these
In July 1973, an AEC Task Group was appointed by the Director,
Division of Operational Safety of the AEC, to review NVO-140 and to
prepare cleanup and rehabilitation recommendations. Members of the
we ee
AEC TASK GROUP REPORT: JULY 1973-JUNE 1974
75
levels.
In commenting on the April 1974 draft, one AEC office expressed the
belief that the plutonium cleanup could be generally characterized as
‘‘reduction of plutonium contamination accessibility’? and recommended
that no numerical guides be published for residual plutonium levels in soil
except those essential for guidance of a group of experts in the field to