Dosimetry
Personnel monitoring devices called Thermoluminescent dosimeters (TLDs) are used to detect and measure external radiation exposures to occupationally exposed workers. TLDs are integrating detectors; that is, they accumulate the radiation dose and give off an amount of light (when properly heated) which is proportional to that dose. The energy absorption properties of TLDs are very similar to tissue so they are used widely as personnel dosimeters. These devices are used to measure exposures from x-ray, gamma ray and high energy beta particles. TLDs are not suitable for measuring exposures to low energy beta particles or alpha particles.
Dosimeters are issued to personnel following a 45 minute orientation and completion of required paperwork. The worker should call the Radiation Safety Division (277-0317) to schedule a time for the orientation. According to 10 CFR Part 19.2, "All individuals working in or frequenting any portion of a restricted area shall be kept informed of the storage, transfer, or use of radioactive materials or radiation in such portions of the restricted areas shall be instructed in the health protection problems associated with exposure to such radioactive materials or radiation, in precautions or procedures to minimize exposure, and in the purposes and functions of all protective devices employed; shall be instructed in, and instructed to observe, to the extent within the workers control, the applicable provisions of commission regulations.... The extent of these instructions shall be commensurate with potential radiological health protection problems in the restricted area."
The orientation will cover topics that the Radiation Safety Division feels the individual needs to be aware of such as dose limits, definitions, radiation protection practices to minimize exposure, procedures used to investigate suspected exposure above established "action limits", information on the dosimetry program, training that may be required, and other related material.
As stated in 10 CFR 20.1502, the requirements for individual monitoring of external and internal occupational exposures are: 1) adults likely to receive in 1 year from sources external to the body, a dose in excess of 10 percent of the limits; 2) individuals entering a high radiation area in which radiation levels could result in a dose equivalent in excess of 100 mrem in 1 hour at 30 centimeters or; 3) individuals entering a very high radiation area in which radiation levels could result in an absorbed dose in excess of 500 rads in 1 hour at 1 meter. In addition, the New Mexico Environment Department requires (Subpart 4) individuals working with medical fluoroscopic equipment to be monitored.
The UNM Radiation Control Committee has determined that any UNM employee who may be occupationally exposed to ionizing radiation shall receive training and, where indicated, a personnel dosimeter.
Internal dosimetry will be provided upon request or when internal deposition is suspected. The mode of uptake may be inhalation, ingestion, injection or absorption. Contact the Radiation Safety Division for appropriate recommendations and/or follow up.