Survey meters should be allowed to stabilize after first turning on for several minutes prior to first use. Further, survey
meters do not instantly indicate the maximum exposure rate because of the response time of electrical components.
Typically survey meters have a response time ranging from 2 to 15 seconds with longer response times being required
for lower dose rates. (For the Victoreen Models 450B, and 450P the response time required to reach 90% of final value
ranges from 2 to 8 seconds and from 1.8 to 5 seconds respectively.) Thus when using the survey meter the operator
must hold the meter in a set position for a period of time longer than the specified response time in order to accurately
measure the actual dose rate present. Survey meter response times are published in the instrument instruction manual.
If a battery indicator is located on the survey meter it shall be checked each time the instrument is turned on. Some
survey meters do not have a battery indicator. However, if the instrument can be zeroed with a zero control, sufficient
battery power is available. Note that the zero will constantly shift on some survey meters, so personnel using these
meters should continually recheck the zero control and adjust the meter as necessary.
Personnel Monitoring Devices.
Personnel who may be exposed to ionizing radiation during the normal course of their duties or occupation SHALL
wear personnel monitoring devices, if directed by the base RSO. Personnel monitoring devices are designed to measure
the total accumulated dose to which an individual is exposed. The devices of most general importance are the
thermoluminescent dosimeter (TLD), the electronic personal dosimeters (EPD), the personal alarming dosimeter (PAD)
or Digital Alarming Dosimeter (DAD) (commonly called a "Chirper"), and the direct reading pocket dosimeter. TLDs
are the primary dosimetry device and have generally replaced film badges as the legal record of radiation exposure in
the Army and Air Force.
Thermoluminescent Dosimeter (TLD).
Theory of Operation.
TLDs are well suited for personnel and environmental monitoring of X-ray and gamma radiation. TLDs are special
materials which, when exposed to ionizing radiation, results in raising the electrons of the detector material to
temporary higher energy states. When these materials are later heated, the electrons fall back to their normal energy
states and in the process emit light. The amount of light emitted is directly related to the amount of radiation dose the
TLD received. By measuring this light, the dose received by the individual wearing the dosimeter can be assessed.
Although a number of materials can be used as TLDs, lithium fluoride, lithium borate and calcium sulfate are the most
common material used for personnel dosimetry.
Control TLD (Or Film Badge).
To accurately measure personnel dose, each radiography area will have at least one device designated as a "Control
TLD/Badge ". It is used to measure radiation exposure received by personnel monitoring devices (primarily from
naturally occurring background radiation) while badges are in storage and transit.
a. The control device will be stored in the same area as the personnel TLD badges away from sources of
radiation in a temperature and humidity controlled area.
b. It SHALL NEVER be worn by any individual.