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Tuesday, 6 December 2011
WASTE CANNISTERS
The waste are securely confined in the cannisters and stored in disposal facilities inaccessible to intruders.
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As we near the end of the century, the disposal of nuclear waste is becoming a concern. Many nuclear power plants around the world are nearing the end of their operating lives.
The disposal of radioactive waste from nuclear power plants and nuclear missiles is as politically intense an issue as the plants and missiles themselves. Yet the three issues have remained curiously separate in spite of their close physical ties. Few debates on nuclear power or nuclear weapons discuss the problems of waste disposal should the power plant or missile be decommissioned.
Nuclear waste can be generally classified a either "low level" radioactive waste or "high level" radioactive waste. Low level nuclear waste usually includes material used to handle the highly radioactive parts of nuclear reactors (i.e. cooling water pipes and radiation suits) and waste from medical procedures involving radioactive treatments or x-rays. Low level waste is comparatively easy to dispose of. The level of radioactivity and the half life of the radioactive isotopes in low level waste is relatively small. Storing the waste for a period of 10 to 50 years will allow most of the radioactive isotopes in low level waste to decay, at which point the waste can be disposed of as normal refuse.
High level radioactive waste is generally material from the core of the nuclear reactor or nuclear weapon. This waste includes uranium, plutonium, and other highly radioactive elements made during fission. Most of the radioactive isotopes in high level waste emit large amounts of radiation and have extremely long half-lives (some longer than 100,000 years) creating long time periods before the waste will settle to safe levels of radioactivity. This area will describe some of the methods being under consideration, for dealing with this, high level, waste. These include short term storage , long term storage, and transmutation.
WASTE CANNISTERS
The waste are securely confined in the cannisters and stored in disposal facilities inaccessible to intruders.
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Fast neutrons produced in the fission reaction are slowed when they bounce off light atoms such as hydrogen or carbon and contains a large amount of such moderating material to slow down the fission neutrons. This takes advantage of the fact that the probability of a neutron being absorbed into another 235U nucleus is much higher at low neutron energy.
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Thermal and fast nuclear reactors
A nuclear reactor converts the fissile components, such as 235U, of nuclear fuel into energy, and fertile components, such as 238U, into fissile components and then into energy. A fissile atom is one that is very likely to be fissioned (split) when a neutron is absorbed, thereby enabling a nuclear chain reaction. A fertile atom is one that can be converted to a fissile atom by absorbing one neutron.In the fission process, which is an exothermic reaction, about 0.09% of the total mass of a uranium atom is converted to energy. Most of this energy is manifested as increased temperature inside the reactor fuel. Liquid heat-transfer material is circulated through the reactor to control the temperature. It also extracts heat for useful purposes, such as to produce steam to drive a turbine connected to an electric generator.
A nuclear reactor converts the fissile components, such as 235U, of nuclear fuel into energy, and fertile components, such as 238U, into fissile components and then into energy. A fissile atom is one that is very likely to be fissioned (split) when a neutron is absorbed, thereby enabling a nuclear chain reaction. A fertile atom is one that can be converted to a fissile atom by absorbing one neutron.In the fission process, which is an exothermic reaction, about 0.09% of the total mass of a uranium atom is converted to energy. Most of this energy is manifested as increased temperature inside the reactor fuel. Liquid heat-transfer material is circulated through the reactor to control the temperature. It also extracts heat for useful purposes, such as to produce steam to drive a turbine connected to an electric generator.
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