Terminology

Activity – This is a measure of the intensity of a radioactive material.
Background Radiation – radiation which is cosmic, naturally present (such as surface rocks), and radon (except as decayed), or other radiation which is not regulated by the Nuclear Regulatory Commission (NRC).
Half Life – The time it takes for half of the activity of a radionuclide to decay by radiation of energetic particles and rays.
Naturally Occurring Radioactive Materials – Any radioactive material in its natural physical state, and not covered under the Atomic Energy Act.
Radiation (ionizing Radiation) – Alpha and Beta particles, Gamma waves, x-rays, neutrons, high-speed electrons, high-speed protons, and other particles capable of producing ions.
ALPHA particles – heavy, positively charged particles emitted by atoms from certain elements. Imparts energy to a relatively small area with a high number of ionizations per unit of tissue impacted. Low penetration characteristics, completely absorbed by the outer dead layer of skin. Not a hazard outside of the body. If inside the body, can directly expose internal tissues and be a hazard.
BETA particles – Positively or negatively charged electrons that are emitted from the nucleus during decay. Have moderate penetration characteristics and can penetrate the skin. They are generally more hazardous when inhaled or ingested.
Gamma Waves – consist of photons emitted from atoms when radioactive materials decay. They impart energy over a relatively large area, pose an external exposure hazard with high penetration characteristics. Damage is less focused but can extend deep into tissue layers.
X-Rays – are similar to gamma waves, in that they cause similar exposure hazards. They are derived from excitation of electrons in a molecule, as opposed to gamma waves which originate from the nucleus of a radionuclide.