2Radioactivity2 Radioactivity is the transformation of an unstable atomic nucleus into one or several nuclei of other elements, and the emission of heat during this transformation as well as an alpha particle (a helium nucleus), an electron (beta particle) or an electromagnetic radiation (X ray or gamma ray).
Radioactive atoms disintegrate according to a specific law. Considering an (n) amount of atoms at time T=0, the half-life is the period of time after which only half of the (n) atoms remain radioactive. The others have disintegrated to create new elements. Not all radioactive elements have the same half-life. Certain half-lives are extremely short (fractions of a second) and others extremely long (4.47 billion years for uranium 238). Carbon 14 is radioactive. Its half-life is 5,730 years. 2Effects on man 2 Ionising radiation, regardless of its origin, natural or artificial, has enough energy to rip electrons from the atoms of the matter it comes in contact with. When it acts upon the components of living cells, it can alter the molecular structures, destroy or modify the cells and, consequently, generate two categories of biological effects.
Certain effects, referred to as deterministic effects (for example burns, nausea etc.) systematically appear, generally early on when the dose of radiation received exceeds a certain threshold, specific to each effect. The seriousness of the damage increases with the dose.
Random effects, referred to as stochastic effects (mainly cancers) appear arbitrarily, always a few years after the individuals have been exposed. The probability of these effects appearing increases according to the dose received but their seriousness is independent of the dose. 2Sources of exposure for man2 Nowadays, 60 to 70% of the radioactivity to which man is exposed is of natural origin. It essentially has four sources:
In France, the average impact of industrial discharge in normal conditions (nuclear reactors, combustible energy, waste treatment) is lower than a few thousandths of the natural radioactivity. The overall balance of the radioactive environment in France, all origins combined, represents an average exposure of 4 mSv per year, of which 2.4mSv is due to natural exposure sources.
Order of magnitude of the natural radioactivity found in certain milieus or products