(Reprinted from Nature, Vol. 202, No. 4934, pp. 745-749,
May 23, 1964)
SPECTROMETRIC DETERMINATION
OF DOSE RATES FROM NATURAL
AND FALL-OUT GAMMA-RADIATION
IN THE UNITED STATES, 1962-63
By WAYNE M. LOWDER, HAROLD L. BECK and
WILLIAM J. CONDON
Health and Safety Laboratory, U.S. Atomic Energy Commission,
New York
” [THE Health and Safety Laboratory of the U.S. Atomic
Energy Commission has boen examining for nearly a
decade the dosimetric properties of environmental radiation, particularly the natural components. Instrumentation and analytical techniques have been developed
which are directed toward securing preciso interpretations
of in situ radiation measurements in terms of air dose
rate!-3, from which quantities of biological interest may
be derived. Because of the importance of total body and
genetic exposure in considerations of the long-term interaction between ionizing radiation and man, our interest
has been focused on the more penetrating radiations.
These include tho y-radiation from potassium-40 and
the daughters of radium-226 and thorium-232 in the
arth and the ionizing component of the cosmic radiation,
consisting primarily of the high-energy muons and
electrons. We have also had to take account of the
presence of fall-out in the environment, and havo devel-
oped techniques for determining the individual dose-rate
contributions to the total environmental y-field of the
various significant natural and fall-out y-emitters. These
techniques are described in this article and a summary
of the field data obtained during 1962 and 1963 is given.
During the late 1950’s, the importance of the y-radiation
from locally deposited fission products from weapons
tests was first noted. Gamma dose rates considerably in
excess of the ambient natural levels were recorded by a
number of investigators either by direct monitoring*‘-* or
by inference from soil and/or air sample analyses?-!°.
Similar increases were noted during the testing period
that began in September 1961 (refs. 11-14). Under such
conditions, ionization chambers have proved valuable as
monitors of changes in total environmental radiationlevels at individual locations, particularly when the
mean natural radiation-levels are known from readings
taken during periods of little or no fall-out‘-*!4. Other
techniques are needed if such readings are not available
or if it is desired to survey newlocations.