-4fastened on top for improved protection from the environment (rainfall,
dirt).
A calibration of the dosimeters was made with a
to deployment.
137
Cs source prior
At each of 80 locations, two TLD badge sets were positioned
] meter above the ground on a slotted crossbar mounted on a wooden stake.
One
of these sets at each location was surrounded with an additional 860 mg/cm*
aluminum attenuator to allow only the energetic gamma component to be recorded
by the dosimeter.
An array of TLD dosimeter badges surrounded by various
attenuator thicknesses was also positioned at a height of |] meter at each of
seven locations to determine the effect of ground cover on the beta
contribution.
An aluminum framework 46 cm wide, 92 cm long and 1 meter high
was used for these experimental stands.
Three pieces of aluminum bar stock
were each drilled to house four sets of TLD badges with various amounts of
aluminum shielding, and bolted across the top of each stand.
Twelve TLD badge
sets were therefore used at each location, shielded top and bottom by various
aluminum absorber thicknesses.
Control TLD sets were stored inside a lead pig
on a southern island with minimal radioactivity.
All TLD badge sets were
retrieved approximately three months later and transported back to Lawrence
Livermore National Laboratory inside a lead pig for evaluation.
A second
calibration was carried out before evaluation to determine fading and transit
exposure.
A pancake GM probe with a 7.62 cm diameter thin window, lead gamma shield and
digital readout was used for comparative purposes.
Measurements with this
portable active instrument were made at 34 locations.
At each location, two
measurements were made at 1 meter height; one with no attenuator and one with
an 860 mg/cm* attenuator over the window.
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