Radiological Safety Traning for Uranium Facilities
Module 104 - Internal Dose Control
Direct or In Vivo Measurement
Direct measurements are performed using whole body counters or lung counters. These
instruments detect gamma and X rays emitted from radioactive material inside the body.
For example, the 235U and uranium-234 (234U) isotopes of uranium present in enriched
uranium emit X rays that can be detected. Alpha and beta radiation emitted by material
inside the body is shielded by body tissue and cannot be detected.
Direct measurement is useful for detecting uranium that is not easily eliminated by the
body. This method may also be used to estimate an internal dose. Because of the very
low energy and intensity of gamma radiation emitted from depleted uranium, direct
measurements ar e not effect ive in detecti ng depleted ur anium in the bod y.
Internal Dose Reduction and Control Techniques
The hierarchy for minimization of internal dose is given in the RCM, Article 316. Engineering
controls should be the primary method of minimizing airborne contamination and internal
exposure to workers, where practicable. Administrative controls, including access controls and
specific work practices, should be used as the secondary method to minimize internal exposure.
If the potential for airborne radioactivity still exists after engineering and administrative controls
have been applied, respiratory protection should be considered. Other specific controls, such as
stay times, worker safety, comfort, and efficiency, are also discussed in Article 316.
The internal exposure resulting from uranium entering the body can be properly controlled by
appropriat e facility an d equipment des ign, contaminat ion control procedures, and protecti ve
clothing. A bioassay monitoring program to determine the amount of uranium taken into the
body is also an integral part of internal exposure control.
Contamination Control Philosophy
The control of contamination in the work place is a significant part of the overall
radiological protection program at uranium facilities. Proper contamination control will: