In order to further compare the results of our low level
measurements to those of other investigators using different
types of instruments, a number of measurements were made in
low level counting rooms at the Lawrence Radiation Laboratory,
Rice University, and HASL.
These measurements substantiated
our confidence in the response of our instruments under such
conditions.
Study of B-ray Ionization Intensity
The high activity of beta-emitting fallout isotopes
such as 90Sr, 144ce, and 106Rh present in the soil during
recent years has stimulated our interest in examining the
free air dose rate and skin and gonadal doses due to f-rays.
We had not considered this aspect of environmental radiation
to be important in past studies and our equipment is
designed not to respond to f-rays.
Since ionization
intensity measurements made by the NYU group with their
1
relatively thin plastic-walled (1/4" plexiglass) chambers*
include a contribution from B-rays, the difference between
their measurement and a measurement made with our instruments
when corrected for the wall thickness of their chamber should
‘roughly indicate the free air B-ray ionization.
Such measure
ments can also be compared with theoretical estimates of the
free air dose rate from B-ray emitters in the soil.
Thus a
series of experiments and theoretical studies in conjunction
with the NYU group were initiated.
In conjunction with these
studies the NYU group made simultaneous ionization chamber
Measurements at several of our field locations during this
cross country trip and also at several sites in the New York
City area.
Section IV.
These B-ray studies are discussed further in
Special Studies
Correlation with Neonatal Death Rate and Birth Weight Several measurements were made at sites in Western Nebraska
to provide Grahn of Argonne National Laboratory with
additional information on natural gamma dose rate levels
for use in his studies of the relation between ionizing