What is Uranium?

What is uranium?

INTRODUCTION | HEALTH

All the uranium on earth was formed aeons ago in the cores of giant stars. At the end of their lives, these stars explode, scattering the heavy elements they have created into the interstellar medium. When our sun was born four and a half billion years ago, this ancient dust was drawn into the planets as they formed, so along with the more common elements such as silicon, iron and oxygen that make up our world, we inherited a blend of more exotic substances. The heaviest among them was uranium.

Uranium is found in trace quantities around the world, but in only a few places is it found in concentrated deposits or ores. The world's richest deposits are found in Saskatchewan, (Canada), Australia and in parts of Africa.

Uranium occurs in nature as a blend of three similar types, or isotopes. The most common type of uranium found in natural deposits is U-238, which makes up 99.27%. The rest is a mix of U-235 (0.72%) and U-234 (trace quantities). Most atomic power stations use enriched uranium, where the more useful (fissionable) U-235 atoms are concentrated to make up a larger proportion of the mix.

Uranium isotopes are radioactive. The nuclei of radioactive elements are unstable, meaning they are transformed into other elements, typically by emitting particles (and sometimes by absorbing particles). This process, known as radioactive decay, generally results in the emission of alpha or beta particles from the nucleus. It is often also accompanied by emission of gamma radiation, which is electromagnetic radiation, like X-rays.

These three kinds of radiation have very different properties in some respects but are all ionizing radiation -- each is energetic enough to break chemical bonds, thereby possessing the ability to damage or destroy living cells.

Uranium-238 emits alpha particles which are less penetrating than other forms of radiation, and weak gamma rays. As long as it remains outside the body, uranium poses little health hazard (mainly from the gamma-rays). If inhaled or ingested, however, its radioactivity poses increased risks of lung cancer and bone cancer.

Uranium is also chemically toxic at high concentrations and can cause damage to internal organs, notably the kidneys. Animal studies suggest that uranium may affect reproduction, the developing foetus, and increase the risk of leukemia and soft tissue cancers.

Summary of Uranium Isotopes
Isotope	Percent in natural uranium	No. of Protons	No. of Neutrons	Half-Life (in years)
Uranium-238	99.284	92	146	4.46 billion
Uranium-235	0.711	92	143	704 million
Uranium-234	0.0055	92	142	245,000

Uranium core sample,
Yeelirrie

the Anti-Nuclear Alliance of Western Australia
email robin@anawa.org.au