120
exposure period for background
determination.
110
The background
exposure was essentially all contributed by cosmic radiation during the
3-month exposure period and during
Additional TLD's were stored on
a
|
@
2
the periphery of the lead pig to
6
identify possible inadvertent
The average background
exposure for the two types of TLD's
5
=
9
2
was subtracted from all field
measurements so that the results
represent only the terrestrial
radiation exposure rates.
100
c
the aircraft flight to LLL.
exposures.
>
0
We
found that sunlight had a negligible
effect on this packaging arrangement.
t
0
|
!
40 50 60
|
70
80
lon chamber response — uR/h
Fig.
2.
Comparison of responses of
the Nal scintillator and the
The correspondence between the
pressurized ion chamber.
results obtained with the Nal
scintillator and the pressurized
10 20 30
linear, deviates more markedly from
ion chamber is presented in Fig.
2.
the 1:1 relationship.
The TLD results indicated that
The ion chamber readings have been
reduced by 3.3 uR/h, the cosmic-ray
the CaF. TLD's overresponded by
contribution at that latitude.
approximately 21% relative to the LiF.
The
figure shows that the NaI scintilla-
This is consistent with similar
tor overresponded because of its
studies made at Enewetak atoll? and
nonlinear energy characteristics.
with environmental monitoring per-
The discontinuity at about 30 uR/h
formed by LLL in the U.S.
occurs at a range switching point
response varies with energy and this
on the scintillator.
ratio (1.21) corresponds to an
Three locations
The over-
were measured on both low and high
average gamma energy of about 500
range, and those results are
keV.
shown in solid circles.
On the
This is reasonable based on
the CaF,
2
enhanced low-energy response
137...
scintillation instrument's low
and the predominance of
range of 0 to 30 uR/h, a correspondence
activities distributed in the soil.
near 1:1 is observed.
range,
On the higher
the correspondence, though
To assess
the beta contribution
to the LiF exposure rates, various