radguide

41 Radiation for Radionuclide Users Personnel Monitoring The assessment of an individual’s cumulative dose from external and/or internal radiation exposure is based upon the use of various procedures and devices for monitoring these exposures. Dosimeters Devices use to measure an individual’s cumulative external radiation dose are called “dosimeters”. The most commonly used dosimeter in research laboratories is the film badge . This consists of a small piece of radiation-sensitive film placed in a special holder containing various filters. The film badge is worn by the researcher ( e.g., usually on the upper torso near the lapel ) whenever working with or near radioactive materials emitting penetrating radiations (i.e., energetic beta particles or gamma rays). On a periodic basis, the film in the badge is replaced and the exposed film forwarded to the vendor’s laboratory for analysis. The amount of darkening of the film can then be measured and used to determine the dose received. TLDs are small chips of material (e.g., LiF or CaF 2 ) which, when heated after an exposure to penetrating radiation, give off light in proportion to the dose received. In research laboratories, TLDs are commonly used within rings worn by individuals handling relatively large quantities of energetic beta or gamma emitting radionuclides (e.g., 32 P, 125 I). Bioassays Assessing the dose from internal radiation exposure is far more difficult than the determination of the dose from an external exposure. Procedures for this purpose are collectively termed “bioassays”. For many water soluble compounds of low energy beta emitting radionuclides (e.g.. 3 H. 14 C), the bioassay consists of a urinalysis utilizing liquid scintillation counting. For radioiodines, internal doses are best assessed by using a NaI scintillation probe to externally measure the radiation coming from the thyroid. Recording of Monitoring Data The federal and state regulations require monitoring of any radiation worker who could possibly receive 10% of any annual occupational dose limit in normal job duty. Annual reports of occupational doses must be given to those individuals meeting this monitoring requirement. A report of annual occupational doses must be given to the monitored individual upon termination or upon request by that individual. All monitored personnel must receive an annual occupational dose