Direct or In Vivo Measurement

DOE-HDBK-1113-98

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: