120
exposure period for background
determination.
The background
0
Nal scintillator response — uR/h
exposure was essentially ail contributed by cosmic radiation during the
3-month exposure period and during
the aircraft flight to LLL.
Additional TLD's were stored on
the periphery of the lead pig to
identify possible inadvertent
exposures.
The average background
exposure for the two types of TLD's
was subtracted from all field
100
90
80
70
measurements so that the results
represent only the terrestrial
radiation exposure rates.
0
We
found that sunlight had a negligible
“effect on this packaging arrangement.
Fig. 2.
The correspondence between the
results obtained with the Nal
0
10 20 30 40 50 60 70 80
lon chamber response — uR/h
Comparison of responses of
the Nal scintillator and the
pressurized ion chamber.
scintillator and the pressurized
linear, deviates more markedly from
ion chamber is presented in Fig. 2.
the 1:1 relationship.
The ion chamber readings have been
.
The TLD results indicated that
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 Nal scintilla-
This is consistent with similar
tor overresponded because of its
studies made at Enewetak Ato11+ and
nonlinear energy characteristics.
with environmental monitoring per-
The discontinuity at about 30 UuR/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.
the CaF, enhanced low-energy response
On the
This is reasonable based on
scintillation instrument's low
and the predominance of 1376.
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