Radiation

• Alpha particles produce much greater ionisation density than beta particles or gamma rays.
• One of the effects of radiation is used in a detector of radiation.
• Radiation can kill living cells or change the nature of living cells.
• One medical use of radiation is based on the fact that radiation can destroy cells.
• Initially the spent fuel rods are stored in cooling p onds.
• The drums are then stored in vaults.
• The water removes some of the heat and also absorbs the radiation.
• The fuel rods are then removed and sealed in drums.
• One use of radiation is based on the fact that radiation is easy to detect.
• The activity of a radioactive source is the number of nuclei decaying in one second.
• Activity is measured in becquerels (Bq), where one becquerel is one radioactive nucleus decaying in one second.
• The absorbed dose is the energy absorbed per unit mass of the absorbing material.
• The gray (Gy) is the unit of absorbed dose and one gray is one joule per kilogram.
• A radiation weighting factor is given to each kind of radiation as a measure of its biological effect.
• The equivalent dose is the product of absorbed dose and radiation weighting factor and is measured in sieverts (Sv).
• The equivalent dose rate is the equivalent dose per unit time.
• The risk of biological harm from an exposure to radiation depends on the absorbed dose, the kind of radiation, the body organs or tissue exposed, and other factors.
• The activity of a radioactive source decreases with time.
• The term ‘half-life’ is used in radioactive decay.
• The principles of a method for measuring the half-life of a radioactive source can be explained.
• The safety procedures necessary when handling radioactive substances can be described.
• A corrected count rate is the count rate from the radioactive source alone, after taking into account the background count rate.
• Artificial (man-made) sources of radiation include medical examinations, fallout from weapons testing, average job, radioactive waste, and others such as TV, aeroplane trips, etc.
• Workers in the radiation industry are allowed to receive an annual equivalent dose of 50 mSv over and above that received from background radiation.
• The annual equivalent dose that a person in the United Kingdom receives from natural sources is about 2 mSv.
• An annual equivalent dose of 5 mSv over and above that received from background radiation is allowed for the general public.
• The half-life of a radioactive source can be found from a graph of activity against time.
• The background count rate is the number of counts recorded in a given time, such as the number of counts per second or the number of counts per minute.
• The main sources of natural radiation that we are exposed to on the Earth are radon and thoron gas from rocks and soil, gamma rays from the ground, cosmic rays, and radioactivity in the human body.
• The nuclear industry adds very little to the level of background radioactivity.
• Cosmic rays contribute to a high radiation dose, especially if you fly a lot.
• Different radioactive materials have different half-lives, for example, Carbon-14 is 5,715 years and Francium-223 is 20 minutes.
• Background radiation is mainly natural radioactivity that is all around us.
• Equivalent dose rate is the equivalent dose per unit time.
• The annual equivalent dose from some sources of artificial radiation is 278 µSv.
• The half-life of a radioactive source is the time taken for half the number of radioactive nuclei present to disintegrate.
• The equivalent dose is reduced by shielding, by limiting the time of exposure or by increasing the distance from a source.
• The radioactive hazard sign and its location should be described.
• The equivalent dose (E) is the dose equivalent to a specified radiation type, measured in Sv.
• The unit of equivalent dose is the sievert (Sv), 1 sievert= 1 joule per square meter (1 Sv= 1 J m - 2 ).