Topic 11-Ionising Radition Flashcards
What is radioactive decay?
Radioactive decay occurs when unstable atomic nuclei decay, by the emission of alpha particles, beta particles and gamma rays. Radioactive decay is random in nature - you cannot tell if any one particular atom will decay, but if you have a large number of the same atom can tell the proportion of atoms that will decay in a given time. As a result of this random nature, if we are going to do an experiments involving the measurements of radioactive decay, we must take repeat reading over lengthy periods, and then an average results.
What is radiation?
Radiation is the general term used to describe the emission of electromagnetic spectrum waves and the energy given out by radioactive materials.
Ionising radiation is the term given to the short-wavelength parts of the electromagnetic spectrum (ultraviolet, X-ray and gamma) and radioactive emissions of alpha, beta and gamma radiation. These types of radiation have such high energy that they can cause atoms to become charged (ionised) by removing electrons. If it occurs inside living cells, the cells can mutate (and possibly cause cancer) or die.
What is perpetrating power?
Alpha, beta and gamma radiation can be distinguished from each other by their penetrating power into different materials. Alpha radiation is the least penetrating and is stopped by a thin sheet on paper or a few centimetres of air. Beta radiation is stopped by a thin sheet of paper or a few millimetres of aluminium, and gamma rays are the most penetrating, have the ability to pass through several centimetres of lead.
Gamma rays, being the most penetrating, generally pass straight through our bodies, causing little damage. Alpha radiation causes the most damage if it gets inside the body as it is absorbed easily by the cells in our bodies.
Where does ionising radiation come from?
Ionising radiation is naturally all around us. We are constantly surrounded by radioactive atoms that can decay admitting alpha, beta or gamma radiation. This can come from our food, building and the ground, in addition to the ionising radiation coming from space (collectively called cosmic rays).
There is also background radiation coming from human-made sources.
Nuclear medicine, X-ray, nuclear power and reprocessing plants, and nuclear weapons explosion all contribute towards the total background radiation. Most of our total background radiation, through, comes from the rocks and soil around us. There contain uranium atoms that decay to eventually from radon gas, which is radioactive, and we breathe it in.
How do we measure the amount of radiation?
We measure the amount of radiation we receive using the concept of dose.
What is nuclear waste?
The waste materials produced by nuclear reactors will remain radioactive for a very long time. About 0.8% of a used (or spent) fuel rod is uranium-235, which remains radioactive for millions of years. In fact, it takes about 703,800,000 years for a sample of uranium-235 to become half as radioactive. It takes about five times this value similar I naturally occurring background radiation. This means that radioactive nuclear waste must be stored for very long time inside very secure storage facilities with thick, lead lined, concrete walls, to prevent alpha, beta and gamma radiation from escaping into the atmosphere. Underground storage may be the only solution.
What is does?
Dose is measure of how much energy we receive from the ionising radiation - and it depends on the local background radiation.
What do we have to take into account before we do an experiment about radioactive decay?
If we are going to do experiments involving the measurement of radioactive decay we must take this background into account. Before we do any experiments we must measure the local radioactive background count and then subtract this value from any counts that we subsequently make.
