Made with Xara Talk to us and ask the expert:       Email  Welcome to Operational Radiation Safety “Πάν μέτρον άριστον” Answers to Frequently Asked Questions (FAQs) What is Radiation? Radiation is a form of energy transmitted through the air. There are many types of radiation that we come across frequently in everyday life, such as heat,  light, radio-waves, microwaves and X-rays. Some radiation types, associated with nuclear and atomic processes, have the ability to penetrate material and in  doing so cause a process called ionization to happen. These radiation types are known as ionizing radiation; they are the ones commonly referred to just as  "radiation" and are associated generally with nuclear and atomic facilities and activities. The source of such radiation is either from radiation generators  (such as x-ray machines) or from radioactive material. Radioactive material occurs in nature, but can also be produced artificially - large amounts are  produced by the operation of nuclear reactors. There are a number of different types of ionizing radiation having different powers of penetration and causing  different rates of ionization in material. The most widely known types of radiation are X-rays, gamma rays, beta radiation, alpha radiation and neutron  radiation. Different types of radioactive material emit these radiation types with differing intensities and differing energies. The radioactive material can be in  many physical forms (it can be solid, liquid or gaseous) - and it can be in many different chemical forms.  The rate at which a radionuclide disintegrates (becoming less radioactive) is characterized by the concept of radioactive half-life-the time it takes for an  amount of radioactive material to decay from its original radioactivity to one half of that amount (T 1/2 ). Depending on the radionuclide this can vary from  fractions of a second to millions of years.  How is radiation measured? Because radiation can penetrate materials and cause ionization within material, it is very easy to measure, even at very low levels. Radioactive material in  some sort of medium (such as air, water, soil, grass, foodstuffs, tissues and so on) can also be collected and the quantity of radioactivity measured and  expressed as a concentration (e.g. radioactive dust can be collected on an air filter for which the total air flow that passed through is known; the amount of  radioactive material on the filter is measured; and hence the concentration of radioactive material in the air where the sample was taken can be calculated.   How are people exposed to radiation?  There are basically two ways that people can be exposed to radiation: they can be exposed externally to a close source of radiation or they can be exposed  internally by radioactive material that has entered the body.                                                           FUKUSHIMA Click to the most up to date site: