PART B: OBTAIN DOSE RATE READINGS
AND COMPUTE TRANSMISSION FACTOR
The reduction in the amount of radiation received by personnel in a shielded environment can be
calculated by the application of a transmission factor. Transmission factors are obtained by dividing the
shielded radiation dose rate by the unshielded or outside radiation dose rate. As an example, if the
outside dose rate is 100 cGy per hour (cGyph) and the dose rate inside an M1A1 Tank is 4cGy per hour,
the transmission factor is obtained by dividing 4 by 100, giving you a transmission factor of 0.04. With
this knowledge, a commander can determine the total dose personnel will receive in shelters or in
vehicles.
To explain the difference between total dose and dose rate, the following definitions are given:
Total Radiation Dose. The total amount of ionizing radiation absorbed by tissue or any other absorbing
material; commonly measured in cGy.
1.
Obtain Dose Rate Readings.
In order to compute the transmission factor in the field, you must have two dose rate readings taken
within 3 minutes of each other. One dose rate reading will be an outside (unshielded) dose rate reading
and the other reading will be taken inside (shielded) the vehicle, structure, or fortification. As was
taught in Part A, the inside dose rate reading should be taken at the position of the most exposed
occupant in combat vehicles, and at the approximate center of structures and fortifications. When taking
readings inside structures and fortifications, the AN/VDR-2 RADIAC Set should be held about one
meter off the floor with the face of the meter up. While holding the radiacmeter in this position, turn
slowly in a complete circle and record the highest reading. The outside reading must be taken at least 10
meters from any obstruction.
2.
Compute Transmission Factor.
Once you have obtained an outside and an inside dose rate reading, the transmission factor is computed
using the formula:
or TF = ID/OD. This formula may be rearranged to determine the inside or outside dose rate.
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CM2308
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