Fact Sheet

Given the concerns surrounding recent uranium exploration in Eastern Ontario and Western Quebec, this Fact Sheet is intended to serve as an educational document to put these activities in a wider context and to allow for greater transparency in the political decision-making process.

Uranium is widely found in trace quantities in rocks in Canada and elsewhere in the world. A few places, such as Australia and northern Saskatchewan, have large quantities of high grade uranium ore, that is, large amounts of rock with very high concentrations of uranium (as high as 20%). Uranium found in rock on both sides of the Ottawa River is somewhere between 0.1 and 0.2%.

Uranium as a pure element exists naturally in three forms: uranium-238, uranium-235, and uranium-234. Each of these forms, called isotopes, acts chemically similar for the most part, but has a different number of neutrons in the nucleus of the atom.

These three isotopes of uranium have the following characteristics:

Percent in
natural
uranium
Number
of protons
Number
of neutrons
Half-Life
(in years)
Uranium-238: 99.27% 92 146 4.46 billion
Uranium-235: 0.72% 92 143 704 million
Uranium-234 0.0055% 92 142 245,000

Each of these three isotopes is radioactive. When a mineral is radioactive, it means that the nucleus of each atom is unstable and, by giving off particles, it is transformed into other elements. Radioactive decay is a spontaneous process in which an atom of one element decays or breaks down into a different element or isotope by losing atomic particles, that is protons, neutrons or electrons. This atomic decay process is often accompanied by a release of penetrating electromagnetic energy in the form of gamma radiation, which is similar to X-rays.

When two neutrons bound together with two protons are released in radioactive decay, this cluster is called an alpha particle. A released electron together with a neutron changing into a proton is called a beta particle. As radioactive particles are given off, the number beside the next element in the sequence decreases to indicate a lower atomic structure.

Each of these types of radiation, that is, alpha, beta and gamma radiation, have the power to break down chemical bonds and thereby damage or destroy living cells. Alpha particles can be blocked with something as thick and heavy as a sheet of paper or skin and are thus mainly a threat when inhaled or ingested. Although they do not penetrate far because of their large mass, alpha particles plough into adjacent living tissue with a great deal of energy and cause major disruption to cells. Beta particles (electrons) can be blocked by something as thick and heavy as sheet aluminum. These particles can penetrate tissue a bit further than alpha particles but have less mass. They can cause damage to the skin and in the body when ingested. Like X-rays, gamma rays can pass through more than a foot of solid rock. Gamma rays can penetrate from an outside source into organs deep within the body, and require lead shielding to reduce exposure.


Uranium-238, the most common form of uranium, has a half-life of 4.46 billion years. That is, half of the uranium atoms in any sample will decay in 4.46 billion years. Uranium-238 breaks down by giving off alpha particles to become Thorium-234. Thorium-234 breaks down through beta emission to become Proactinium-234. Proactinium-234 decays through further beta emission to become Uranium-234. The various decay products form a series starting with Uranium-238. After several more alpha and beta decays, the series ends with the stable isotope Lead-206. See sidebar.