The use of radioactivity and nuclear physical processes - for example nuclear fission in nuclear power plants - is widespread today

Nuclear physical processes play a role in our daily lives. Protection from the resulting radiation is possible and resulting radioactive wastes have to be isolated safely from the human environment on the long term.

Radioactivity is used mainly in the following areas:

Radioactive substances are used for materials testing, level measurements and density measurements (radiometry) and for process control.

They are also used in measurement technology and analytical procedures, for example for detecting water damage, drugs and explosives.

Various everyday objects also contain radioactive substances. Small amounts make fluorescent substances in paint light up, for example in old watches, display units or compasses. Older generation smoke alarms function with radiation sources.


Testing welding seams on a pipeline. Image: Suva


Radioactive substances are used in medicine as radiopharmaceuticals or radiation sources in clinical examinations (diagnosis) and treatments (therapy).

Radiation levels are low in most applications. Radiation from strong sources (or from X-ray apparatus) is used only for killing cancer cells (tumours) or sterilisation of medical equipment.


One example is tomography. In this method, the patient takes glucose that is marked with a radioactive substance that is then distributed throughout the whole body. Radiation is then used to identify and image the location and structure of organs, tissue and tumours.

Positron emission tomography (PET) is used to measure the radiation of an administered radiopharmaceutical. This can be used to identify small metastases of tumours as their cells concentrate the radioactive tracer more strongly than healthy cells (Image:© Grieze |


Cancers are treated using strong external radiation sources that are specifically targeted to kill tumours. Alternatively, weak sources are used over longer times directly in the body, for example in cervical cancer. Radioactive medications are also used.

Radiotherapy in the treatment of cancer is very advanced. It can be used with high accuracy to avoid damaging healthy surrounding tissue.

Electricity and geothermal heat thanks to uranium

Nuclear fission in nuclear power plants

Electricity production in nuclear power plants relies on nuclear fission of uranium. One kilogram of fissile uranium can produce around two million times more energy than the equivalent amount of petroleum.

Switzerland has five nuclear reactors that produce practically carbon dioxide-free electricity. Generation of nuclear electricity produces radioactive waste. 40 percent of the total electricity production in Switzerland comes from the nuclear power plants and 60 percent from hydropower. The hydrological cycle in the atmosphere required for this (evaporation, increase in humidity and precipitation) is driven mainly by the thermal radiation from the sun, which itself is the result of a nuclear physical process (nuclear fusion).

One of Switzerland’s five nuclear reactors is located at Leibstadt. Nuclear fission takes place in the reactor housed in the spherical building. Image: Kernkraftwerk Leibstadt

Geothermal heat

Geothermal heat is produced mainly by the decay of natural radioactive substances in the earth’s crust. Together with the original heat from the earth’s core and solar radiation, it brings the surface to a temperature that is capable of sustaining today’s biodiversity.


In Switzerland, geothermal heat is exploited widely using borehole heat exchangers and heat pumps. The potential for geothermal power plants for electricity production is also being investigated.

Ionising radiation is used in fighting pathogens and in agriculture

It is also used worldwide for sterilisation of medical equipment or implants.

The fight against the tsetse fly, a carrier of the sleeping sickness, involves sterilising specially bred males using radiation and releasing them in large numbers. The same method is used to control pests in agriculture.

Radiation sources are also used to kill bacteria such as salmonella, and to extend the shelf life of foodstuffs such as spices and seeds. A company in Switzerland also has a permit for irradiating dried herbs and spices.

Radioactive substances are used in a wide range of research fields; they are also produced by irradiation with particles

There is a research reactor at the EPFL (Ecole polytechnique fédérale) in Lausanne.

The Paul Scherrer Institute (PSI) in Villigen/Würenlingen and the European Organization for Nuclear Research (CERN) in Geneva use particle accelerators as research tools. In these cases, radioactivity is produced by the irradiation of specific components with particles.

Radioactive materials are used in numerous applications. Radioactive tracers are used in chemical research and for investigating the transport of toxic substances underground or the movement of sediments in rivers and in the sea. Old works of art are cleaned of insect and fungal attacks by irradiation. Radiation sources in space probes produce the energy required for the long journey into space.

Various naturally occurring radionuclides with different half-lives can be used for determining the age of archaeological finds, rocks and groundwaters using the proportion of the decaying radionuclides to their daughter products.

European Organization for Nuclear Research (CERN) Image: CERN

Applications of radioactivity

Image: Comet / W4