Nuclear
Radioactivity and population:
what are the sources, what are the risks?
Le 18/08/2011
When we hear the word radioactivity, we often think of nuclear testing, power plant accidents and radioactive waste. However, radioactivity is a natural phenomenon present everywhere on earth. And most artificial radioactivity emitted by human activity comes from medical uses. What levels of radioactivity are we exposed to on a daily basis? Are there any risks involved? Planète Energies takes a comprehensive look at the issues.
cooling towers and their steam plume at the Areva site
of the Tricastin nuclear power plant, the largest uranium
enrichment site in Europe.
© AFP - P. Desmaze
How to measure radioactivity?
Three different units are used to express radioactivity:
• The becquerel (Bq) measures the amount of radioactive material emitted by a source.
• The gray (Gy) expresses the dose absorbed by living organisms (which depends significantly on the length of exposure).
• The sievert (Sv) measures the biological effects of radiation (which differs depending on the type of radioactive elements and on the organs affected).
Radioactivity is all around us
Natural environmental radioactivity
Radioactivity is a natural phenomenon that occurs everywhere: in the ground, rocks, ambient air, water and also living organisms. Radon from the earth’s crust can enter houses via the ground, walls, service mains, etc.
Some regions are naturally more radioactive than others. Granite regions, for example, have higher radioactivity than sedimentary basins because granite contains uranium and radium.
In all, the average natural radioactivity in France is about 2 millisieverts (mSv) per year.
Radioactivity produced by human activity
Artificial radioactivity is also a source of radiation. This is the case with medical radioactivity, primarily radiology for X-rays and scanners, but also radiotherapy and the sterilization of medical equipment.
The fallout from nuclear tests carried out in the atmosphere, from the Chernobyl accident in 1986 (the 2011 Fukushima accident is “invisible” in mainland France), from industrial discharge or radioactivity produced for industrial applications such as ionization are all other sources of artificial radiation.
In all, in France, average exposure over one year to artificial radioactivity is about 1.5 mSv.
Examples of X-ray radiation
In Archeology, X-rays can also be used to safely analyze precious or fragile objects.
The impact of nuclear power plants is 500 times less than natural radioactivity
In contrast to what is widely believed, nuclear power plants only add a tiny amount of radioactivity to the environment (excluding accidents).
In fact, in France as a whole, average radioactive discharge from nuclear power plants does not exceed 0.002-0.004 mSv/year, 500-1,000 times less than average natural radioactivity in France.
Radioactivity: its effects on health
Ionizing radiation causes damage to DNA, which the organism may or may not be able to repair. The harmful effects of radioactivity on health depend on a variety of factors such as type of radiation, chemical characterization of the radioactive element, length of exposure, affected organs, etc.
The effects actually caused are also proportional to the dose received:
• Below 100 mSv, no harmful effect has been demonstrated to have taken place;
• Between 100 mSv and 500 mSv, the risk of developing cancer increases proportionally with the dose. These are random, long-term effects;
• Above 500 mSv, acute radiation occurs, although this rarely happens. This type of radiation, the severity of which increases with the dose, has an almost immediate effect (between several days and a few weeks) and is inevitable.
