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Radioactivity & exposure

Radioactivity is a natural phenomenon. Our body receives a dose of 'ionizing' radiation every day, from the earth and from the cosmos

The best-known application of radioactive material is probably the production of electricity in nuclear power plants. But medicine and the industrial sector also use radioactive materials and ionizing radiation, e.g. for radiotherapy, medical isotopes, food sterilization, or to measure welds in the construction sector. In addition, there are centres that conduct research into radioactive material.

Irradiation and contamination

The chance of a serious accident in a nuclear site is small, but not non-existent. In such an accident there may be radioactive material released in the air, in the water or on the ground.

You can’t see, smell, taste or feel radioactivity. You can only detect radioactive materials with specific measuring equipment.

In case of radioactive substance release there is a chance of contamination or irradiation:

  • Contamination: radioactivity from contact with radioactive materials
    • Internal: when the substances have been ingested into the body via inhaled air, by eating contaminated food, or drinking contaminated water
    • External: when the radioactive substances come into contact with skin, hair or clothes
  • Irradiation: radiation from remote radioactive sources, without direct physical contact


Specific signs of exposure (vomiting, burns, massive hair loss...) occur only after a massive exposure to radioactive material and over a certain time (from a few minutes to a few weeks depending on the radiation dose). Such an exposure can only be expected a priori among workers present in the facility where the accident occurs, and possibly among the first responders.

The risks for the population in case of nuclear accident are mainly long-term risks (cancer and genetic abnormalities). The chance of complications (but not their severity) increases in function of the exposure dose to the radiation.

Because of this risk, the government and the operators of nuclear sites monitor the safety on a daily basis and work together to reduce the risk to a minimum. Among other activities, they implement strict controls and prepare contingency plans and procedures, which they can apply if an incident does occur.

More information

Radioactivity: always and everywhere (SCK-CEN)