the
s, 24Na,
7
counts to
peak
comparison
r using
These
these isotopes and the response data given in Tables I,
counts/ (ur/hr - 238U) and 1300 counts/ (ur/hr - 232Th).
similar correction of 350 counts/(ur/hr - 232Th)
must be
A
| made to the 0.51 MeV peak before estimating the 106Rh dose
the
rate.
Energy Band Method
le.
is
£ the
imate of
slightly
chemes
RF
Le aA IT
esponse
In determining natural emitter dose rates, the total
"energy" (counts per channel multiplied by mean y-ray energy
corresponding to that channel) in the spectrum between energy
values that bracket significant peaks is related to the total
dose rate contribution from the emitter or series of emitters
characterized by these peaks.
The three bands used are
centered about the 1.46 MeV peak (49K), the 1.76 MeV peak
(214pi-238u series),
/T) 3
II
qd
of
Ss, are
for the
areas
continuum,
(Np/T)
higher.
nproved
c
and
II,
and III these correction factors were determined to be 3000
two
ber
ral
the 0.61 Mev
the area of the entire smeared-out peak and subtract a
contribution based on the ?38y and 232Th dose rates determined
from higher energy peaks.
From the decay scheme data for
smaller.
Yr source
es
and overlaps
the 137cs dose rate, therefore, it is necessary to estimate
ntegration
for these
stribution
angular
energies
rate,
1s often much larger than
peak, and we cannot separately determine the areas of these
two peaks or the 0.58 MeV 2087) peak.
In order to estimate
1 Mev
thus
The new detectors are able to resolve the 0.66 Mev 13/’cs
At present however, the 0.66 MeV
and 0.61 Mev 214Bi peaks.
an
tion, the
1.76 MeV
je 1.46
and the 2.62 MeV peak (20871-232tmseries).
As in the 5" x 3" detector calibration,
three simultaneous
equations relating the "energy" in the bands EF), 1.32 - 1.60
MeV; E>, 1.62 - 1.90 MeV; and E3, 2.48 - 2.75 MeV to natural
emitter open field dose rates were derived by applying a
multiple regression analysis to the peak area estimate of
the dose rates and Ej, E92,
and E3 for a large number of field
locations.
The cosmic ray contribution to each energy band
was first subtracted out using crystal response data from
Spectra taken over large lakes at different altitudes.
Section III and Figure 3)
(See
The resulting equations for the 4" x 4" detectors with
bakelite shields are
K
U=
.O78E]'
.337E9'
T =
.297E3'
-
.055E9'
.179E3'
-
.022E3'