Technological Hazard

Technological Hazard >> Radiation hazard >> Interaction radiation with matter

Ionizing radiation is produced by radioactive decay, nuclear reactions, like nuclear fission or nuclear fusion, and by particle accelerators that may produce, e.g., fast electrons produced bremsstrahlung or synchrotron radiation. The energy of radioactive decay is emitted as radiation in three main forms: alpha particles, beta particles and gamma rays.

In order for radiation to be ionizing, the particles must both have a high enough energy and interact with the atom. Charged particles such as beta particles (electrons or positrons), and alpha particles interact strongly with atomic electrons. Neutrons, on the other hand, do not interact strongly with electrons, and so they cannot directly ionize atoms. They can interact with atomic nuclei, depending on the nucleus and their velocity, these reactions happen with fast neutrons and slow neutrons, depending on the situation. Neutron radiation often produces radioactive nuclei, which produce ionizing radiation when they decay.

Gamma quanta do not ionize all along their path like alpha or beta particles . They interact with atomic electrons by one of three effects: photoelectric effect, Compton effect, or pair production. In every scattering event, the gamma quantum transfers energy to an electron, and it continues on its path in a different direction with reduced energy. When the energy from radiation is absorbed by matter, chemical changes occur at the atomic level. If the exposure is large enough these changes can be readily observed. For example, if glass is heavily irradiated it changes colour. The amount of radiation absorbed per gram of matter is called the absorbed dose.

An ionization event normally produces a positive atomic ion and an electron. The negatively charged electrons and positively charged ions created by ionizing radiation may cause damage in living tissue.

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