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l          What is “Radiation”?

 

All matters in this world are made up of tiny particles called atoms.  Every atom has a nucles and a surrounding cloud of electrons.  When an unstable nucleus undergoes changes, invisible particles or waves are released. The particles and waves are called radiation.  The unstable nucleus is said to be radioactive.  The radiation which removes orbital electrons from atoms, thus creating ion pairs, is called ionizing radiation.  If the ionization process occurs in living tissue, chemical changes would damage the cells and can lead to injury in the organism.

 

In a typical fission process in a nuclear power plant, an incoming neutron hits a uranium 235 atom to produce two lighter fission products together with some energy in the form of nuclear radiation and between 2 to 3 neutrons for further fission reactions.

 

Ø            Types of Ionizing Radiation

 

1.            Alpha particles – swiftly moving nuclei of helium atoms with positive charges.

2.            Beta particles – high speed electrons with more penetrating power than alpha particles.

3.            X-rays and gamma rays – penetrating rays passing through body.

4.            Neutrons – carrying no charge but with high penetrating power.

Common Types of Ionizing Radiation

Image Credit: Government Information Services, HKSARG

 

Ø            Sources of radiation

 

There are two generic sources of radiation – natural and artificial.  Natural radiation includes cosmic ray from space and radiation emitted by radioactive substances that exist on food and habitat.  Artificial radiation comes from radioactive fallout from nuclear testing, x-rays emissions from vacuum tubes, such as medical diagnostic machine, television and video display units, and use of radioactive materials in consumer products such as smoke detectors.