Internal Dose Measurements - hdbk1113cn10139

DOE-HDBK-1113-98

Radiological Safety Traning for Uranium Facilities

Module 104 - Internal Dose Control

limiting. For chronic exposures, chemical toxicity is more limiting up to 1.3% enrichment.

Beyond 1.3%, th e effective do se equivalent becomes limitin g.

Internal Dose Measurements

Once in the body, the presence of uranium can be detected using indirect radioactivity

measurements, direct radioactivity measurements, or both.

At one time, it wa s not possibl e to detect in ternal upta kes of uranium or certain othe r radioacti ve

materials at levels below the point at which the annual limit for exposure (5 rem) was received.

Any measurable intake of uranium was therefore considered to be unacceptable. Improved

analytical and calculational techniques have now made it possible to measure uranium

concentrations resulting in exposures of about 10 mrem with a reasonable degree of accuracy.

The estimation of low-level internal exposure to uranium is no longer a matter for inordinate

concern.

Indirect or In Vitro Measurement

Bodily processes will, to some degree, eliminate uranium taken into the body. How

effective the body is at eliminating the uranium, and how long the process takes, depends

upon individual metabolism and the chemical form of the uranium. For example,

uranium hexafluoride contains uranium that is chemically bound to fluorine and is more

easily eliminated than uranium metal or uranium dioxide.

Indirect measurements are made by sampling material eliminated by the body for the

presence of uranium. It is possible to analyze both feces and urine for the presence of

uranium, but due to the ease of collection and handling, the most common method used

is urinalysis.