Radiation is all around us in nature. Our earth and even our own bodies emit radiation. Everyone is constantly exposed to natural radiation. This has always been the case. Only when modern science developed instruments that could measure radiation did we become aware of it.

Ionising radiation

You cannot see, hear or smell radiation. The consequences of a harmful dose of radiation do not manifest themselves until months or even years later. But not all radiation is harmful. There are different kinds of radiation: non-ionising and ionising radiation. Examples of non-ionising radiation are: visible light and radio waves. Radioactive materials emit ionising radiation. Because of this very characteristic these materials are used often. But this characteristic also makes radioactive material dangerous. When radiation is emitted this brings about a change in the atomic structure of the radioactive material. Eventually a new atom is created which is no longer able to emit any radiation and thus is no longer radioactive. The radioactive material has decayed.

Different types of radiation

Radioactive materials emit different kinds of radiation: alpha, beta and gamma rays. Radiation can, however, be stopped. The penetrating power of alpha rays is very low and can be stopped by as little as a piece of paper. Beta rays have slightly more penetrating power; they can be stopped by a 1 cm layer of water. Gamma and X rays have more penetrating power. Materials such as concrete, iron or lead are the most effective in shielding against this radiation.

Doses of radiation

The amount of radiation, or radiation dose, is expressed in milliSievert (mSv). In the Netherlands everyone receives a natural radiation dose of about 2 milliSievert per year as a result of natural sources of radiation. Depending on their living environment, radiation doses show an average variation of about 0.2 milliSievert per year for people in the Netherlands. Acceptable levels of radiation caused through the use of radioactive materials are laid down by Dutch law. The storage of radioactive waste at COVRA results in a dose much lower than 0.2 milliSievert per year at the site boundary; much lower than the variation in the natural radiation dose.


Spanjeweg 1
4455 TW Nieuwdorp
The Netherlands

Havennummer 8601

E-mail: info@covra.nl
Tel: +31(0)113 616 666 Fax: +31(0)113 616 650

Contact us