Radioactive substances are among the most toxic materials known. The magnitude of their harmful effects is so great that they could figuratively be described as a "quantum leap".
The origins of radioactive pollution
H.P. Jammet, Head of the Atomic Hygiene and Radio Pathology Department of the French Atomic Energy Commission, defines environmental radioactive pollution as "the increase in natural background radiation resulting from human activities involving the use of natural or artificially produced radioactive materials. The atmosphere filters out much of the sun's radiation, including most of that which would be lethal to life.
Naturally occurring radioactive elements are present in rocks, water and air, and in all living organisms. The composite of all forms of natural radiation to which we are exposed is called background radiation. For millions of years, background radiation has remained at a relatively constant level. These naturally occurring radioactive elements include radon: a gas produced by the breakdown of uranium impossible to detect without a suitable deviceThis is a common feature in French homes.
Recently, however, the radiation to which we are normally exposed has increased and is expected to continue to increase. Man-made radiation includes radiation from X-ray machines, radioactive fallout, nuclear reactors, research laboratories, industrial and medical uses of radioactive materials and radioactive waste from the production of radioactive materials.
Environmental radiation can be divided into two types: natural and man-made.
Radiation of natural origin
Natural radiation is :
- Cosmic radiation from outer space reaching the Earth's surface.
- Terrestrial radiation from naturally occurring radioisotopes in the earth's crust. The bombardment of the atmosphere by cosmic rays continuously produces some radioactive material with a short half-life. The half-life of a radionuclide is its radioactive half-life and affects the length of time a radioactive substance can remain active as an environmental pollutant.
Man-made radiation comes from human activities involving the use of radioactive materials. They are used for the production of nuclear weapons, nuclear fuel and electrical energy.
One of the most harmful uses of radioactive materials is in nuclear weapons, particularly atomic bombs. The world has already seen the nature of destruction and the impact of radioactivity on humans and the environment during the Second World War, when atomic bombs were dropped on Hiroshima and Nagasaki, two Japanese cities.
Increased radiation levels in the environment
Over the past forty years, there have been a number of nuclear weapons tests at sea or on land, which have resulted in increased levels of radiation in the environment. A study has revealed that the radioactive materials that cause these explosions are fission products such as strontium 90, caesium 137, iodine 131 and unused explosives. These elements are deposited in soil or water or remain suspended in the atmosphere, thus becoming a major cause of radioactive pollution.
The nuclear fuels used in the operation of reactors also contribute to radioactive pollution. The heat released during the fission and activation process is converted into electricity. During this process, two types of waste are formed: fission products remaining in the primary and secondary fuels and foreign activation products in the coolant.
Disposal of radioactive or nuclear waste is a big problem and a cause of environmental pollution. It includes metal products left over from the mines, fission products and activation products. These fall into three categories: low-level waste, intermediate-level waste and high-level waste. Of these, the high-level products remain in the environment for several hundred years.
Similarly, leaks in nuclear reactors often become the cause not only of environmental pollution, but also of the death of hundreds of people, as was the case with the leak in the atomic reactor at Chernobyl in the former USSR on 26 April 1986.