Nuclides/isotopes and uses of plutonium - DOE-HDBK-1145-2001

Radiological Safety Training for Plutonium Facilities

DOEHDBK11452001

Student's Guide

C. Natural plutonium

The half-life of plutonium is so short compared to

the age of the earth that if plutonium had existed when

the earth was formed, plutonium would not exist today.

So, for all practical purposes, plutonium must be man-

made.

Remnants of a natural reactor have been

discovered in Africa, and it is believed to have

operated for millions of years. Very small traces of

plutonium have been found in uranium ore, resulting

from cosmic-ray produced neutron bombardment of

uranium.

II. Nuclides/isotopes and uses of plutonium

A. Predominant plutonium isotopes

Atoms of a specific element can exist in several

forms. The difference between the forms is the

number of neutrons in the nucleus. These forms are

called isotopes of an element. An analogy is that ice

cream can come in several flavors, but it is still ice

cream. Most elements in nature have several different

isotopes. (They have the same number of protons, but

a different number of neutrons). Plutonium has 15

isotopes.

Nuclide is a broader term than isotope and refers to

any combination of protons and neutrons that exists in

more than a transient state. An isotope is a specific

combination of protons and neutrons, which defines it

as a subset of an element; the two need to be

referenced together, such as "an isotope of plutonium."

The predominant nuclides are Pu-238, Pu-239, Pu-

240, Pu-241, and Pu-242. Each has a specific

application.