Radiological Safety Training for Uranium Facilities
Module 101 - Properties of Uranium
I. MODULE 101 - Properties of Uranium
Describe the physical, radioactive, toxicological, and chemical properties and biological
effect s of uran ium.
B. Physical Properties
Uranium can be encountered as a solid, liquid, or gas, depending on its chemical form and
surrounding conditions. Each of these physical forms has particular hazards. Sometimes, changing
the form of uranium can lead to radioactive decay products accumulating or becoming concentrated
in a particular location, such as on the surface of a liquid. The result can be an apparent increase in
the radioac tivity.
The solid forms of uranium are generally the most stable configurations. The shiny, silvery
metal form is rarely seen except in a workshop when it is being machined. After machining, the
surface oxidizes, typically within hours, to a hard, black surface.
After some time, depending on temperature, humidity, and alloy, the surface may change color
and begin to flake. Orange or yellow co lored su rfaces are usua lly more fl aky and sol uble. In
these forms, co ntamination c an be more easil y spread, inhal ed, and absorb ed into the bod y.
Uranium melts at 1133°C, so molten uranium is unusual, except in a foundry. It has often been
observed that the radioactivity appears to increase when uranium is melted. This is because
radioactive decay products, such as radium and thorium, float to the surface. The density of
radium is 5 g/cm3, compared with 19 g/cm3 for uranium; therefore, radium floats in molten