Chemical Reactivity - hdbk1113cn10121

DOE-HDBK-1113-98

Radiological Safety Training for Uranium Facilities

Module 101 - Properties of Uranium

it is removed from the body with a biological half-life varying between 6 and 5000 days,

depending on which organ has become contaminated. Uranium tends to concentrate in the

kidneys and the bones. Additionally, if inhaled, the lungs are exposed. Internal exposure to

uranium is controlled by limiting the ingestion and inhalation of this element. These methods,

along with measurement techniques, are discussed in Module 104.

Most heavy metals, such as uranium, are toxic to humans depending on the amount introduced

into the body. For short-term (acute) exposures, the toxicological effects are the primary

concern, and acute exposures to significant amounts of uranium may result in kidney damage.

However, as the enrichment of the uranium in the 235U isotope increases, so too do the effects of

radiation exposure in relation to toxicological effects.

Past industrial experience has proven that if there is a long-term exposure of small amounts of

uranium (chronic exposure), the radiological effects are the primary biological concern. In fact,

for chronic exposures, a development of tolerance against the toxicological effects may occur.

The princi pal radiolo gical hazard as sociated wit h uranium is due to the relati vely high energy

alpha particles its radionuclides and daughters emit. A chronic exposure to these radionuclides

result in an increased risk of cancer, typically in the bones, kidney, and lungs, since these are the

organs where uranium is deposited.

3. Chemical Reactivity

The chemistry of uranium is complicated. For example, uran ium forms several oxides: UO, UO2,

UO3, and UO4. In general, a sample of uranium oxide will include a mixture of several of these.

For example, U3O8 is sometimes written as (UO2)C2(UO3).

The lower oxidation states, UO2 and U3O8, tend to be dark brown or black. The higher oxidation

states, UO3 and UO4, are generally orange or yellow, especially in solution or if water or

crystallization are present (e .g., UO4C2H2O). Furthermore, the higher oxides usually flake off

more easily and are usually more soluble in water. Being flaky, they are more easily inhaled.

Being more solubl e, they are more ea sily absorbed into the body.