Extinguishing Plutonium Fires

PYROPHORIC METALS

DOE-HDBK-1081-94

Spontaneous Heating and Pyrophoricity

Extinguishing Plutonium Fires

Plutonium fires should not be approached without protective clothing and respirators

unless the fire is enclosed in a glove box. The most effective agent for extinguishing

plutonium fires has been found to be magnesium oxide sand. Glove boxes which

contain pyrophoric forms of plutonium should also contain an amount of magnesium

oxide adequate for extinguishment. The burning plutonium should be completely

covered with the sand to as great a depth as possible. The magnesium oxide

extinguishes the fire by providing a heat sink which cools the plutonium and by

providing a barrier which limits the availability of oxygen.

Argon is a very effective extinguishing agent, providing the oxygen content in the

atmosphere is maintained at 4% or less. Above 4% oxygen, flooding with argon will

not extinguish a plutonium fire. This is an important point, since it is nearly

impossible to reduce the oxygen content to 4% or less during argon flooding in most

fume hoods. Argon may be used effectively to cool the burning plutonium prior to

application of the magnesium oxide sand.

Other agents have been tested for use on plutonium fires; however, none have proven

to be as effective as magnesium oxide. Typical foam or dry chemical agents are not

effective extinguishing agents. Fusible salt agents have been shown to be effective on

small-scale plutonium fires. However, the expansion which accompanies the oxidation

of plutonium has caused the fusible salt coating to crack, allowing the plutonium to

re-ignite.

Water is generally acceptable for use as an extinguishing agent for fires involving

plutonium. In rare cases where criticality safety considerations preclude the

introduction of moderators such as water, suitable alternative fire protection

measures need to be incorporated into the facility design. Proper housekeeping which

includes removal of combustibles from pyrophoric forms of plutonium is the most

important aspect of fire loss minimization.

Uranium

Properties

Nonenriched uranium is a radioactive metal that is also combustible. Its radioactivity

does not affect its combustibility, but can have a bearing on the amount of fire loss.

Most metallic uranium is handled in massive forms that do not present a significant

fire risk unless exposed to a severe and prolonged external fire. Once ignited, massive

metal burns very slowly. In the absence of strong drafts, uranium oxide smoke tends

to deposit in the immediate area of the burning metal. Unless covered with oil,

massive uranium burns with virtually no visible flame. Burning uranium reacts

violently with carbon tetrachloride, 1,1,1-trichloroethane, and the Halons. For power

Pyrophoricity

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