Beta and Gamma Comparative Dose Estimates on Enewetak Atol]
K. W. Crase, P. H. Gudiksen, and W. L. Robison
ABSTRACT
Enewetak Atoll
is one of the Pacific atolls used for atmospheric testing of
U. S. nuclear weapons.
Beta dose and gamma ray exposure measurements were
made on two islands of the Enewetak Atoll during July-August 1976 to determine
the beta and low energy gamma contr ibution to the total external radiation
doses to the returning Marshallese.
Measurements were made at numerous
locations with thermoluminescent dosimeters (TLD), pressurized ionization
chambers, portable Nal detectors, and thin-window pancake GM probes.
Results
of the TLD measurements with and without a beta attenuator indicate that
approximately 29% of the total dose rate at 1 meter in air is due to beta or
low energy gamma contribution.
Studies on the effect of ground cover on this
contribution indicate that it is relatively insensitive to thickness of ground
cover.
Integral 30-year external shallow dose estimates for future inhabitants were
made and compared with external dose estimates of a previous large scale
radiological survey (EN73).
Integral 30-year shallow external dose estimates
are 25 to 50% higher than whole body estimates.
Due to the low penetrating
ability of the betas or low energy gammas, however, several remedial actions
can be taken to reduce the shallow dose contribution to the total external
dose,
“Work performed under the auspices of the U.S. Department of Energy by the
Lawrence Livermore National Laboratory under contract number W-7405-ENG-48."
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