Potential sources of radiation from industrial applications can be categorized as follows:
- Electrical Power Generation
There are presently about 445 nuclear reactors world-wide which are producing electrical power. Canada is a major producer of fission generated electrical power using heavy water reactors of a uniquely Canadian design (CANDU).
None of the world's reactors contributes radiation to the environment. All radiation is confined to the reactor core and to special radiation containment facilities. Any radiation leaks into the environment, on the rare occasions that they occur, from nuclear power generating facilities are almost always a result of accidents caused by exceeding the design limitations of the facility, inadequate levels of preventative maintenance, or poorly implemented and insufficient staff training.
- Medical
Isotopes are widely used in cancer therapy with considerable success. Very short half-life isotopes are used.
The ideal isotope would be:
- Site specific, meaning that the element used to make an isotope would concentrate itself at the body site selected. For example, iodine tends to concentrate in the thyroid gland, making it a good choice for certain types of cancer therapy.
- Short lived, and with non-radioactive decay products. This would limit the exposure time to which a tissue would be exposed to the highest levels of radiation.
- Highly soluble and with a chemical affinity for compounds that can be "flushed" through the body.
Of course no isotope meets all these criteria exactly so compromises are made to select the best.
The radiation from these sources to the general public is zero, unless one is undergoing radiation therapy.
- Military
During the 1950s and 1960s atmospheric testing of nuclear weapons by both the USA and the USSR led to significantly increased levels of radioactive fallout on a global scale. The vast majority of the radioactivity in the fallout came from isotopes with half-life ranging from minutes to days. Within a few weeks the fallout levels had dropped to levels that were very low and continued to decline. Some isotopes however were not as transient. For example 38Sr90 (strontium-90) with a half-life of 28.1a, is a 546keV beta emitter. Strontium-90 is especially insidious because of its chemical similarity to calcium. Strontium concentrates itself in cow's milk and dairy products. When consumed by children it is further concentrated as it competes with calcium for inclusion into bone tissue.
55Cs135 (cesium-135) whose half-life is 3x106a, is 210keV beta emitter and 55Cs137 (cesium-137) with a half-life of 30.2a, is a 1.18MeV beta emitter whereupon it decays into Barium-137 (with a 662keV gamma ray emission).
Both of these isotopes are rapidly concentrated in the food chain.
By international agreement all nations which possess nuclear capabilities have agreed to a ban on atmospheric tests.
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