Radioactivity is a natural property of certain substances. There are natural and artificial sources of radiation.
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Different types of radiation
Radioactive substances have an unstable atomic nucleus that decays spontaneously. This emits high-energy radiation, colloquially known as radioactive radiation. Humans cannot perceive this radiation with their senses.
The three most important types are:
Radioactivity decreases with time
Radioactivity is constantly decreasing due to radioactive decay. This also decreases the radiation of the radioactive materials and thus the waste until it reaches harmless levels over time. This is why the waste should be disposed of in a deep geological repository to protect people and the environment. Safety barriers reliably enclose the waste there.
Radioactive substances can be ingested through the respiratory tract or with food and then decay inside the body (internal radiation). Protection against internal radiation is achieved by avoiding the intake of radionuclides as far as possible.
Radioactivity in nature
A small amount of natural radioactivity occurs everywhere: in the soil, in building materials, in our food and in the air we breathe. We thus continuously absorb a small amount of radioactive substances into our bodies. For example, potassium-40, which is preferentially incorporated into muscle tissue.
The natural radioactive substances were originally formed in exploding stars (supernovae) and later incorporated into our home planets during formation. Through their decay they contribute significantly to the earth’s heat. To a small extent, natural radioactive substances are still created in the atmosphere today through interaction with cosmic radiation.
Natural radiation: Radon is the front-runner
The average radiation exposure for a person in Switzerland is around 5.8 millisieverts per year. At 4.3 millisieverts, most of it is natural radiation. This includes cosmic radiation from space, which depends on the altitude of the place of residence above sea level. Part of the natural radiation comes from the soil and rock; this part varies depending on the area of the country. The highest exposure, 3.2 millisieverts, is caused by gaseous radon in homes (cf. Figure). It enters the house from underground through natural cellars or cracks, or is released by building materials in the house.
In addition, we are also exposed to artificially caused radiation. Higher exposures come from medical applications, much lower from industrial applications.
Avoiding radiation exposure
Alpha, beta and gamma rays belong to the group of ionizing rays. They transfer so much energy to the atoms and molecules of irradiated matter that electrons are released from their atomic shells. This can lead to the breaking of chemical bonds and thus damage to cells, tissues and organs.
The three types of radiation penetrate human tissue to different depths. Alpha radiation has a short range and can penetrate only fractions of a millimeter into the top layer of skin. Beta radiation has a penetration depth of a few millimeters and can thus penetrate the skin layers. The high-energy gamma radiation penetrates the human body completely. It weakens somewhat, but at the same time scatters in the tissue.
How to protect yourself from radiation
Radiation from natural and artificial sources differs only in its origin, but not in its properties and effects. We protect ourselves from a source of radiation outside the body by shielding the source, keeping sufficient distance from it, and minimizing the time spent near it.
Alpha and beta rays can be completely shielded with relatively little effort. Penetrating gamma radiation can be attenuated by a few centimeters of iron or a few meters of rock or concrete.
Radioactivity is constantly measured
The National Emergency Operations Center (NEOC) operates its own radioactivity monitoring network. 76 probes distributed throughout Switzerland transmit the current measured value every ten minutes. On the NAZ website you can find the daily averages and time histories.