Download
1 / 15
160 likes | 580 Views
Nuclear Fission. Richard Miller 5SJW. The History of Nuclear Fission. In 1935 Enrico Fermi discovered that numerous useful radionuclides could be made by splitting up an atom with neutrons.
E N D
Nuclear Fission Richard Miller 5SJW
The History of Nuclear Fission • In 1935 Enrico Fermi discovered that numerous useful radionuclides could be made by splitting up an atom with neutrons. • Hahn and Strassman then learnt about the benefits of fission with Uranium, which caused a self-sustaining chain reaction of fission processes releasing a huge amount of energy. • Niels Bohr then found out that this happened because the extra neutrons sent the nucleus into a severe vibration that split open the atom, causing the fission process.
What is Nuclear Fission? • In a nuclear power station, free neutrons in a reactor core are manipulated so that they embed within the nucleus of a Uranium atom. • This causes great instability within the Uranium and it splits into at least two uneven atoms, as well as an entirely random assortment of gamma rays, alpha and beta particles and extra neutrons. • These extra neutrons cause a chain reaction, and many sets of daughter atoms of the original Uranium atom experience fission. This releases a huge amount of energy.
Fission Fuels • A Fission Fuel is a substance that can elicit a great amount of energy through splitting by fission. • Such fuels are all heavy and fissile (capable of chain-reaction fission). The three most common fuels are: a) Uranium 233 b) Uranium 235 c) Plutonium 239 • All these fuels possess the four major traits required to be a useful Fission Fuel: a) Exceed the binding energy level required to disassemble a mass. b) Release 2+ extra neutrons per fission stage. c) Have a long half life. d) Readily available for mining.
Nuclear Reactors • This is a centre for the initiation of controlled chain fission reactions. • There are several different designs for reactors; shown left is a Magnox reactor named after Magnesium, the metal used to hold the Uranium control rods in place. Graphite is used as a moderator (mediums that convert neutron energy from kinetic to thermal, a process that causes a prolonged chain fission) and Carbon Dioxide is used as a coolant.
Nuclear Reactors (continued) • The basic way in which a reactor works is shown by the diagram on the left. • High in energy neutrons are supplied by the fuel rods. There are three possible ways in which fission may take place. • a) A neutron is fired and simply embeds in an atom within the fuel rods. • b) A neutron is blocked off by a control rod, slowing it down and then being embedded. • c) The moderator reduces the K.E. of the neutron, increasing the chances of it being embedded. • Whichever way the fission takes place, it then initiates a long chain of reactions that releases a large amount of energy. • The energy created is used for the same sort of things that any other power plant is used for. It is converted to electricity in order for this to happen.
Fast Breeder Reactors • A fast-breeder reactor is a special reactor that produces more of a fissile element that it consumes, as well as energy. • This means that once set up, it is hugely economical, because the by-products of reactions can be used over and over again. • Combinations of highly fissile fuels are used, for example 20% Plutonium Dioxide and 80% Uranium Dioxide is commonly used. • They do not use moderators, as with regular power stations. Instead, they rely upon the high speed of neutrons to maintain a chain reaction. • They are unfavourable because the risk factor of them is potentially greater than that of a nuclear bomb. They are also more dangerous and less reliable than standard reactors. Occasionally, Plutonium 240 is produced and this contaminates the fuel and makes it difficult to use.
Dangers of Nuclear Fission • The number of safety and insurance regulations concerning nuclear reactors show how dangerous they are. • The reactivity of the core must be carefully controlled, so that a number of neutrons that will release a steady amount of energy are being fired. Should too many neutrons be released, the energy surge would be so great that an explosion would be likely. • The core must be kept cool. In the fission, a lot of thermal energy is released, meaning that the reactor gets very hot. Should the core become excessively hot, the pressure would increase and it would become highly dangerous. • Barriers preventing radiation must be well maintained. The gamma rays produced by fission are very dangerous, because they can ionise with skin and cause mutations. Therefore concrete shielding is required to be maintained to a high level. • Risks of explosions are of concern with Nuclear Power, for example at Three Mile Island in America Gamma rays’ powers to mutate means that nuclear power is commonly associated with cancer, as found also in America.
Nuclear Power – the way forward? • This has caused great controversy among many people. • I have tried to come to my own conclusions concerning this matter with information I have gathered over the next few pages. I am Tony Blair, PM of England Nuclear Power is on my agenda for England's’ power!!
Conclusions • With fossil fuels beginning to run out, Nuclear Energy could be a vital source of fuel in the future. • However, the health implications that surround it mean that it is dubious whether or not it is the ideal power of the future. Overall, I believe that if Nuclear Power is managed carefully and factories are commissioned only in very sparsely populated areas to minimize health problems, it could become a very useful energy resource in some fields in the future.
George Best Manchester United Legend 1946-2005 R.I.P.
