Decay Series - doe-hdbk-1113-98_reaffirm_2005

DOE-HDBK-1113-98

Radiological Safety Training for Uranium Facilities

Module 101 Properties of Uranium

Both alpha and beta particles are emitted as part of decay series. For example,

U decays by alpha emission to 234Th; 234Th decays by beta emission to

238

234mPa; and so on, until stable 206Pb is finally reached.

1. Decay Series

Uranium has two naturally occurring decay series: the "actinium" series, which

has 235U as its parent; and the "uranium" series, which has 238U as its parent.

Many of our everyday encounters with radioactivity come from these decay

series; examples are radon gas and radium. There are also man-made isotopes of

uranium - 232U and 233U. The decay products from these radionuclides must

be considered in the implementation of a radiological control program at a

facility where these uranium nuclides are present.

2. 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