Internal Dose Measurements - hdbk1113cn10078

DOE-HDBK-1113-98

Module 104 Internal Dose Control

Lesson Plan

Instructor's Notes

The amount of uranium retained in the lungs depends a

great deal on the size of the particle breathed. The smallest

particles tend to be exhaled or absorbed into the

bloodstream, while the largest particles are usually removed

before they re ach the lung. Ura nium retained in the lungs

may remain there or be absorbed into the bloodstream. Part

of the uranium passing through the digestive tract may also

be absorbed in the bloodstream. Uranium in the

bloodstream is either transferred to various organs or

excreted via the urine.

The enrichment of the uranium in its 235U isotope als o plays

a role in determining whether the radiological or the

chemical effects are the limiting factor. For acute

exposures, chemical toxicity is limiting up to 39%

enrichment. Beyond 39%, the effective dose equivalent

becomes limiting. For chronic exposures, chemical toxicity

is more limiting up to 1.3% enrichment. Beyond 1.3%, the

effective do se equivalent becomes limitin g.

Highlight the internal exposure

Internal Dose Measurements

measurements used at your

facility.

Once in the body, the presence of uranium can be detected

using indirect radioactivity measurements, direct

radioactivity measurements, or both.

At one time, it was not possible to detect internal uptakes of

uranium or certain other radioactive materials at levels

below the point at which the annual limit for exposure (5

rem) was received. Any measurable intake of uranium was