Los Alamos.
Ata distance of 200 cm, no permanent neutron damage occurred. During the
time period when the dose rate was within the recording range of the instrument, no transient
blackouts or spurious signals were recorded. Calibration of the instruments was accomplished
at Los Alamos using a 100-curie Co®™ source. The resulting calibration curve (frequency versus
xr/hr) for a representative instrument is presented in Figure 2.9. Geometry considerations
dictated the positioning of the probe from 10 to 170 cm from the source to achieve the desired
dose rates.
Frequency versus time was recorded on the Ampex tape recorder from time zero to H + 60
seconds.
In order to change this frequency to a voltage necessary to drive the Bristol chart
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Figure 2.7 Kaiser dose-~rate instrument, oscillator and compression circuit.
recorder, the system illustrated in Figure 2.10 was used. The curves produced on the Bristol
recorder chart served as calibration checks.
-.
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The two types of recorders in Steps 1 through 5 (Figure 2.10) were used to stretch the time
scale by a factor of sixteen. The signal output from Step 5 was amplified, clipped, and differ~entiated in Steps 6 through 8 in order to accurately trigger the one-shot multivibrator in Step 9.
The output pulses from the miltivibrator were of constant amplitude and width but with a repetition rate equal to the input triggering signal. These signals were integrated and then recorded
on the Bristol chart recorder as voltage versus time in Steps 10 and 11.
2.2.2 Film. Film was used to record the total gammadose at the stations indicated in Table
2.1. Standard NBS film holders (including Kodak 548-0 and Dupont 553, which contains D502,
D510, and D834 film) and Lexington Signal Depot film packs and film stacks were used as shown
in Table 2.1.
.
The Lexington Signal Depot calibrated the film exposed in their holders using Co®’, The
sources of radiation used to calibrate the NBS film packets were a 500-curie Co® source at
EG&G and a 7-curie Co® source at Kirtland Air Force Base.
The 500-curie source was encased in a uranium Shield.
from a window at the front of the shield.
The source was located 24, inches
The window could be removed and the source rotated
19