Fire - hdbk1113cn10120

DOE-HDBK-1113-98

Radiological Safety Training for Uranium Facilities

Module 101 - Properties of Uranium

1. Fire

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

byproducts.

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,