There are three types of radiation emitted by radioactive isotopes.
- Alpha particles (α)
- Beta particles (β)
- Gamma rays (γ)
Alpha (α)
*Alpha particles are helium nuclei, with a positive charge and little penetrating ability.
Alpha particles consist of two protons and two neutrons. They can be stopped easily, human skin or a few sheets of paper. If alpha particles enter the body(ingestion) it can be hazardous. An example is americium-241, used in smoke detectors.
Beta (β)
*Beta particles are electrons, with a negative charge and greater penetrating ability than alpha particles.
In some radioactive elements, neutrons disintegrate into protons and electrons. The electrons -β particles are emitted from the atom fast. They can be stopped by 2-3 mm thickness of aluminium. An example is Carbon-14 which is used in dating of artefacts.
Gamma (γ)
*Gamma rays are high energy electromagnetic radiation, with greater penetrating ability than beta and alpha.
This type of radioactivity is emitted by isotopes in a form of rays. They have no mass or charge. They move very quickly and have a strong penetrating ability. A thick shield of concrete or lead can stop them. An example is cobalt-60 which is used in cancer treatment and food irradiation.
Half-life t½
*The half-life of a radioactive isotope is the time taken for half of the atoms in a sample of the isotope to decay.
Different elements have different half lives. For example: Carbon-14 has a half-life of 5,730 years. Uranium-238 has a half-life of 4.5 billion years! For a radioactive atom to fully disintegrate it must go though 10 and a half half-life's
Background Radiation
We are all exposed all the time to some radiation, called background radiation. It is natural and fund from:
- Cosmic Radiation
- Rocks-containing traces of uranium and its decay product Radon. Granite rock releases Radon. It can accumulate in houses to levels that increase of lung cancer.
- Man made radioactive materials.
Natural Radiation
- 87% of background radiation.
- Produce natural radiation.
- Many radioactive atoms that once existed have now emitted radiation and have now become non-reactive.
- Examples, Uranium, Radon and Thorium.
Radon
Atomic number 86, symbol Rn, noble gas. Radon is responsible for the majority of public exposure ionizing radiation. It is the largest contribution to an individual's background radiation dose and varies from location. Radon is a gas and can accumulate in a building especially in a confined room such as attics. Epidemiological studies have shown a link between breathing high concentrations or radon gas and lung cancer. You can measure radon in your home by placing two small detectors in your home for three months. One is placed in the main bedroom and the other in the living room. After three months the detectors are returned to the lab. A report will be issued indicating the average level of radon and advice on what to do if the level is high.
Links:
http://www.rpii.ie/Measurement-Services/Radon-Measurement/Services/Apply-For-Measurement-Online.aspx
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