Uranium is a naturally radioactive heavy metal that has often been perceived as potentially dangerous. However, we cannot maintain our standard of living without it.

In its pure form, uranium (U) is a silvery metal almost twice as dense as lead. It originated in exploding stars billions of years ago and heat from its radioactive decay is believed to have kept the Earth’s core in molten state. Uranium occurs most commonly in nature in oxide form as pitchblende. Natural uranium consists of three isotopes, U-238, U-235 and U-234, all of which are radioactive but only U-235 is capable of sustaining a spontaneous fission reaction when the critical mass is reached. During groundwater transport, uranium preferentially adheres to soil particles, giving a concentration typically about 35 times higher than that in pore water. Although uranium can bioconcentrate in some biota, it is not known to biomagnify in terrestrial or aquatic food chains.

Uranium occurs in trace amounts in everything we encounter in our daily life, including our own body. The top 1 m of soil in a typical suburban garden in the UK has been reported to contain 2 kg U.

Uranium is less dangerous and more useful than often believed

The hazard of uranium is twofold: 1) the metal itself is toxic, and 2) its natural decay gives rise to ionization radiation, mainly in the form of alpha particles, and unstable intermediate daughter products such as radium and radon. Uranium is a health hazard only if it is taken into the body by ingestion or inhalation. Once ingested most uranium is excreted within a few days while a small fraction (0.2-5%) absorbed into the bloodstream is deposited preferentially in the bone (~22%, where it can remain for years) and the kidney (~12%, where it is discharged in days). Similarly, only a small portion of inhaled uranium usually penetrates to the lung’s alveolar region, where it may be retained for many years.

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For many years, uranium was used to color ceramic glazes and for tinting in early photography. Today its primary use is as fuel in nuclear power reactors to generate electricity. 20 kg of uranium can produce as much energy as 400,000 kg of coal without generating greenhouse gas. Currently, nuclear power accounts for 15% of Canada’s electricity supply. Besides electricity generation, uranium is also used as fuel for smaller reactors to power submarines, ice-breakers, aircraft carriers and different types of space craft. Another important use of uranium is in the creation of radioisotopes for use in medicine, to preserve perishable food items, and are utilized in smoke detectors and also by the police to investigate crimes. Researchers often use radioisotopes to analyze pollutants in the environment and trace their movement in surface and ground waters.

Canada leads the world in uranium production, accounting for approximately one-quarter quarter of the total global output. Uranium mining and milling directly employ over 1,000 Canadians and contribute over $500 million annually to the country’s economy. In 2007, overall uranium exploration expenditures amounted to $350 million across Canada.

Depending on the characteristics of a deposit, uranium is mined by open-pit or underground mining methods or a combination of both in sequence. Although not currently practiced in Canada, in some circumstances low-grade uranium ore can be exploited by in situ leaching. Recently, to reduce the miners’ exposure to radiation, the extraction of high-grade ores in the underground has become more mechanized so that people may not come into direct contact with the ores.