All atoms of the same element have the same number of protons in their nuclei. The number of neutrons, however, may vary. For example, all atoms of uranium have 92 protons. Yet, some atoms of uranium have 146 neutrons, while others have 143 neutrons. Atoms of the same element that have different atomic masses are called isotopes.
About 50 naturally occurring isotopes, including those of uranium and radium, are unstable. This means they emit particles and energy from their nuclei in order to become more stable. Atoms that decay in this way are said to be radioactive. Marie Curie, a Nobel Prize-winning physicist and chemist, was the first person to use the word radioactive to describe an element.
Radioactive atoms give off alpha particles (large particles made of two protons and two neutrons) and beta particles (high-speed electrons.) They also give off electromagnetic energy in the form of gamma rays. These particles and rays given off in the decaying of unstable nuclei are called radiation.
Our concern in Camden is with ionizing radiation; there are three types:
2. Gamma rays.....similar to X-rays, but they are produced by the spontaneous decay of radioactive materials.
3. Particle radiation.....includes alpha particles and beta particles. They are also produced by the decay of radioactive materials.
Gamma Radiation - Gamma Radiation is the major kind of radiation being measured at the contaminated sites in Camden. Gamma radiation results from the breakdown or radioactive materials like uranium, radium and thorium normally found in small quantities in the soil and rock in this area. The manufacturing process at the General Gas Mantle Factory used an ore containing radioactive thorium, to make gas mantles.
Radon and Thoron - Radon is the decay product of uranium. Thoron is one of the decay products of thorium. Both of these are odorless, colorless gases that can accumulate in air and water.
Thoron and Radon Progeny - These are the decay products given off by thoron and radon gas. Radon progeny are the major source of human exposure to alpha radiation. It is this alpha radiation that is responsible for cellular changes in the respiratory tract, which causes radon-induced lung cancer. Consequently, alpha particle exposure, under certain circumstances, can be quite harmful.
Three basic principles are important in protection against radiation:
2. Distance....the further one is from the source of the radiation, the less likely he/she is to be exposed.
3. Shielding.....alpha particles can travel a short distance through air and can easily be stopped by a sheet of paper of the human skin. They are only dangerous if breathed into the lungs of ingested in food or water. Beta Particles can penetrate the skin a short distance; they can be blocked by plastic or wood. Gamma rays can pass completely through the skin and penetrate internal organs; concrete or lead is necessary to block them.
The above text is taken from "Radiation and You - A Health Information Pamphlet", written by the Health Team.