To ensure that exposures are ALARA, National Labs monitor many of its workers to determine the actual exposures received. Most of these individuals are monitored for external or penetrating radiation and wear dosimeters to measure their exposures.

A dosimeter is a device that is worn like a name tag and measures the radiation dose a person receives from external sources. Currently, about one fourth of all Laboratory NukeWorkers routinely wear dosimeters. Dosimeters are replaced and the radiation doses measured monthly or quarterly by the Dosimetry department. Your supervisor will be able tell you whether or not you should be in this program. Even if you are not required to wear a dosimeter in your work area, one can be made available to you upon request.

	Figure 4. Thermoluminescent Dosimeter

The type of dosimeter routinely used at National Labs is a thermoluminescent dosimeter (TLD) (see Figure 4). TLDs contain crystals that absorb energy when exposed to ionizing radiation and release that energy in the form of light when heated to high temperatures at the Dosimetry department. The amount of light released from the dosimeter is proportional to the radiation dose received. It is useful for a broad range of the penetrating radiation fields found at the Laboratory, including beta, gamma, and neutron.

You will receive a radiation exposure report if the dosimeter you wore indicates you received a radiation exposure. All National Lab workers who wear dosimeters are also provided with an annual exposure summary, even if they received no radiation exposure that year. Anyone who has worn a dosimeter at the Laboratories may obtain a copy of his/her exposure report from the Dosimetry department.

A few radiological workers are also monitored for internal doses. A person may receive an internal dose through the ingestion or inhalation of radioactive materials. This monitoring typically focuses on a few individuals who routinely handle dispersible radioactive materials. Dose levels are assessed by measuring radioactivity in urine or by measuring the radiation emitted from inside the body. Positive internal doses are reported to the individual and are included in his or her personnel dosimetry record, in the same manner as exposures recorded by the TLDs.