Radiological Safety Training for Uranium Facilities
Module 101 - Properties of Uranium
Uranium is a metal that will sustain a burning reaction (similar to a magnesium flare). The
potential for a fire is greatest when the uranium is in a finely divided form, such as milling chips
or filings. In this form, uranium can undergo spontaneous ignition. Uranium metal is often
machined to provide a useful end product, and milling chips and filings are unavoidable
Precautions must be taken to prevent chips and filings from igniting. One precaution is
submersing the chips and filings in water or a mineral oil. Storage in water produces hydrogen
gas due to a chemic al reaction . To prevent th e hydrogen gas fro m reaching an expl osive
concentrat ion, and to pre vent a pressur e buildup, con tainers must b e vented. Inciden ts have
occurred where container lids have been blown off by unexpected gas pressure buildup.
Once uranium starts to burn, it is extremely difficult to extinguish. None of the typical
extinguishing methods, such as water, carbon dioxide, or halon, is effective in fighting uranium
fires. In fact, halon may be explosive and produce toxic fumes if used directly on the fire.
Normally, small fires may be put out by using MET-L-X powder, which is a mixture of sodium
chloride (table salt) and potassium carbonate (baking powder). When spread over the burning
metal in significant quantities, MET-L-X starves the fire of oxygen.
Larger fires, such as with storage drums, are more difficult to extinguish. Submersion in water
will eventually work once the metal cools down. However, continuous water addition is
necessary to make up for losses due to boiling and evaporation.
2. Toxicological/Biological Effects
The principal entry of uranium into the human system is due to either inhalation or ingestion.
Inhalation occurs either from release of volatile uranium compound or from suspension of
volatile uranium-laden aerosols. Ingestion can occur when the uranium is introduced into water
for consumption or the food chain by plant uptake. When uranium is either ingested or inhaled,