What is radiation?

1 November 2016

Some people object to nuclear power stations because of a fear of radia­tion. Radiation must be treated with respect, but can be used to the advantage of humankind, as proved by medical X-rays, in the treatment of cancers, and in the preserving of fresh produce.

Radiation is the process whereby certain atoms emit energy in the form of electromagnetic waves or particles in order to become more stable.

Radioactivity is a natural phenomenon. Everything around us is radioactive to a greater or lesser degree. Plants, water, rocks, even the air we breathe - everything contains radioactive substances. This has been so since the creation of the universe. Radiation even reaches us from outer space.

Humans have always been subjected to natural radiation. We are exposed to radiation from the sun and outer space (cosmic rays) and naturally occurring radiation elements are taken into our bodies by means of food and water or by inhalation. Radiation is emitted by the ground, soil and rocks and naturally varies greatly from location to location.

Although the term “radiation” is very broad and includes things such as light and radio waves, it is most often used to mean “ionising” radiation. This is radiation that can produce charged particles (“ions”) in both inanimate and living matter and can present a health hazard depending on the duration and intensi­ty of exposure. There are various types of ionising radiation: alpha, beta, neutron and gamma radiation. Atoms that emit these kinds of radiation are said to be radioactive.

The duration and intensity of radiation exposure determines the effect of radiation. To understand this, think what happens when you spend time in the sun. The longer you stay in the sun and the brighter the sunlight, the more you are likely to be sunburnt. Similarly, the more radiation you receive, the greater the effect. The care taken in designing and licensing a nuclear power station ensures that stations are designed not only to prevent accidents, but to minimise their effects on the populations living around them during normal operation as well as in the unlikely event of a nuclear accident. The licensing of nuclear installations in South Africa is the stat­utory responsibility of the NNR (National Nuclear Regulator).  

The sievert is the unit of radiation that is a measure of the amount of damage on the human body as a result of the absorbed ionising radiation.  The internationally accepted maximum limit of radiation that an individual member of the public is allowed to be exposed to as a result of the operation of a nuclear power station is 1 millisievert (0.001 sievert) in a year. The NNR licence for Koeberg stipulates a maximum dose of 0.250 millisievert per year which is a quarter of the international limit.  This is equivalent to the radiation one is exposed to when one goes on a 100 flights between Cape Town and Johannesburg or undergoing 25 dental x-rays. The exposure from natural background radiation for any member of the public is approximately 3 millisievert per year.

Issued by Eskom Media Desk, 1 November 2016