Chemical Reactivity - doe-hdbk-1113-98_reaffirm_2005

DOE-HDBK-1113-98

Radiological Safety Training for Uranium Facilities

Module 101 Properties of Uranium

radionuclides results 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, uranium 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)2(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., (UO4)

2H2O). 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 soluble, they are more easily absorbed into the body.

Uranyl compounds, such as uranyl nitrate, or UO2(NO3)2, are chemical forms of

uranium that are often found in solution with water. They are generally yellow

in color and are used in criticality experiments.

Uranium reacts readily with air and water. For example, when uranium is

machined, small chips catch fire from the heat of the machining process.

Shavings placed in water react to produce hydrogen gas. The surfaces quickly

oxidize to a hard black coating that is at first protective; however, under adverse

conditions, it corrodes and flakes.

Uranium also reacts with hydrogen or tritium gas to form uranium hydride

(UH3). Uranium "beds" are commonly used to store tritium. Uranium

hexafluoride (UF6) reacts in moist air to produce hydrogen fluoride (HF) gas,