Nuclear Reactions: AN INTRODUCTION TO FISSION, FUSION, AND NUCLEAR POWER
ã Nuclear reactions deal with interactions between the nuclei of atoms ã The focus of this presentation are the processes of nuclear fission and nuclear fusion ã Both fission and fusion processes deal with matter and energy Introduction
Matter and Energy ã Previous studies have taught us that matter and energy cannot be created nor destroyed ã We now need to understand that Matter and Energy are two forms of the same thing
ã Matter can be changed into Energy ã Einsteins formula above tells us how the change occurs ã In the equation above: E = Energy m = Mass c = Speed of Light (Universal Constant) E = mc 2
ã The equation may be read as follows: Energy (E) is equal to Mass (m) multiplied by the Speed of Light (c) squared ã This tells us that a small amount of mass can be converted into a very large amount of energy because the speed of light (c) is an extremely large number
Fission notes ã Fission may be defined as the process of splitting an atomic nucleus into fission fragments ã The fission fragments are generally in the form of smaller atomic nuclei and neutrons ã Large amounts of energy are produced by the fission process
Fission notes ã Fissile nuclei are generally heavy atoms with large numbers of nucleons ã The nuclei of such heavy atoms are struck by neutrons initiating the fission process ã Fission occurs due to electrostatic repulsion created by large numbers of protons within the nuclei of heavy atoms
ã A classic example of a fission reaction is that of U-235: U-235 + 1 Neutron 2 Neutrons + Kr-92 + Ba-142 + Energy ã In this example, a stray neutron strikes an atom of U-235. It absorbs the neutron and becomes an unstable atom of U-236. It then undergoes fission. Notice that more neutrons are released in the reaction. These neutrons can strike other U-235 atoms to initiate their fission. Fission notes
ã The fission process is a natural one. A French researcher found a natural uranium reactor in Gabon, West Africa; it has been estimated to be over 2 billion years old ã Fission produces large amounts of heat energy and it is this heat that is captured by nuclear power plants to produce electricity
ã Fusion is a nuclear reaction whereby two light atomic nuclei fuse or combine to form a single larger, heavier nucleus ã The fusion process generates tremendous amounts of energy; refer back to Einsteins equation ã For fusion to occur, a large amount of energy is needed to overcome the electrical charges of the nuclei and fuse them together Fusion notes
ã Fusion reactions do not occur naturally on our planet but are the principal type of reaction found in stars ã The large masses, densities, and high temperatures of stars provide the initial energies needed to fuel fusion reactions ã The sun fuses hydrogen atoms to produce helium, subatomic particles, and vast amounts of energy
ã Mass and Energy are two forms of the same thing; neither can be created nor destroyed but mass can be converted into energy (E = mc 2 ) ã Fission is a nuclear reaction in which a heavy atomic nucleus is split into lighter atomic nuclei ã Fusion is a nuclear reaction in which 2 light atomic nuclei are combined into a single, heavier atomic nucleus Review notes
Nuclear reaction notes ã Chain reaction occurs when a Uranium atom splits ã Different reactions –Atomic Bomb in a split second –Nuclear Power Reactor more controlled, cannot explode like a bomb
History of nuclear power 1938– Scientists study Uranium nucleus 1941 – Manhattan Project begins 1942 – Controlled nuclear chain reaction 1945 – U.S. uses two atomic bombs on Japan 1949 – Soviets develop atomic bomb 1952 – U.S. tests hydrogen bomb 1955 – First U.S. nuclear submarine
Atoms for Peace Program to justify nuclear technology Proposals for power, canal-building, exports First commercial power plant, England 19561956
ã The energy in one pound of highly enriched Uranium is comparable to that of one million gallons of gasoline. ã One million times as much energy in one pound of Uranium as in one pound of coal. Economic advantages notes
Emissions Free notes ã Nuclear energy annually prevents –5.1 million tons of sulfur –2.4 million tons of nitrogen oxide –164 metric tons of carbon ã Nuclear often pitted against fossil fuels –Some coal contains radioactivity –Nuclear plants have released low-level radiation
Nuclear power around the globe ã 17% of worlds electricity from nuclear power –U.S. about 20% (2nd largest source) ã 431 nuclear plants in 31 countries –103 of them in the U.S. –Built none since 1970s (Wisconsin as leader). –U.S. firms have exported nukes. –Push from Bush/Cheney for new nukes.
Countries Generating Nuclear Power CountryTotal MW USA99,784 France58,493 Japan38,875 Germany22,657 Russia19,843 Canada15,755 Ukraine12,679 United Kingdom11,720 Sweden10,002 South Korea8,170
Nuclear Reactor Process ã 3% enriched Uranium pellets formed into rods, which are formed into bundles ã Bundles submerged in water coolant inside pressure vessel, with control rods. ã Bundles must be SUPERCRITICAL; will overheat and melt if no control rods. Reaction converts water to steam, which powers steam turbine
Back end: Radioactive waste ã Low-level wastes in commercial facilities ã Spent fuel in pools or dry casks by plants ã Nuclear lab wastes –Hanford wastes leaked radiation into Columbia River ã High-level underground repository –Yucca Mountain in Nevada to 2037 –Wolf River Batholith in Wisconsin after 2037? –Risks of cracks in bedrock, water seepage
Radioactive Waste Recycling ã Disposal of radioactive waste from nuclear power plants and weapons facilities by recycling it into household products. ã In 1996, 15,000 tons of metal were received by the Association of Radioactive Metal Recyclers. Much was recycled into products without consumer knowledge. ã Depleted Uranium munitions for military.
ã Nuclear energy has no typical pollutants or greenhouse gasses ã Nuclear waste contains high levels of radioactive waste, which are active for hundreds of thousands of years. ã The controversy around nuclear energy stems from all parts of the nuclear chain. Summary notes
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