Criticality - doe-hdbk-1113-98_reaffirm_2005

DOE-HDBK-1113-98

Module 101 Properties of Uranium

Instructor's Notes

Lesson Plan

Criticality

Uranium is a fissionable material, which means it can

undergo nuclear fission. Nuclear fission is a process in

which a very heavy, unstable atom splits in two, or

"fissions". When an atom fissions, one large atom

primarily becomes two smaller atoms, between one and

seven neutrons are given off which may cause fission in

nearby atoms), and a great deal of energy is given off as

radiation and in other forms, such as kinetic energy of the

fission fragments. The radiation created could result in the

creation of radiological areas, such as High or Very High

Radiation Areas. Nuclear criticality associated with

uranium will be discussed in greater detail later in the

lesson.

Chemical Properties

Uranium is chemically reactive. It burns in air like

magnesium; it is toxic like lead; and it forms a large

variety of chemical compounds. All the isotopes of

uranium have the same chemical reactivity, and all can be

made into the many different physical and chemical forms

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discussed in this section.

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.