nuclear reactions chemistry mrs. coyle. part i fission and fusion
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- Nuclear Reactions Chemistry Mrs. Coyle
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- Part I Fission and Fusion
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- Transmutations When a nucleus of an element is transformed to a nucleus of another element.
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- Transmutations Can occur through: Decay (Spontaneously) Nuclear Reactions (Fusion and Fission)
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- Nuclear Reactions Fission Fusion
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- Nuclear Fission Enrico Fermi (USA) 1930s Lise Meitner, Strassman, Hahn (Germany) Bombarding neutrons at 235 U or 239 Pu causes fission (splitting) of the nucleus producing new neutrons that then cause more fission in a chain reaction. Huge amounts of energy (mostly kinetic energy of fragments) is released
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- Nuclear Fission n + 235 U 236 U X+Y +n + energy Chain Reaction Neutron bombardment
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- Nuclear Fission 235 U is a rather rare isotope(0.7%) of the more abundant 238 U which does not undergo fission. Nuclear Bomb Nuclear Power Plants
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- Nuclear Fusion Suns energy comes from fusing of hydrogen to form helium Product has higher mass number than reactant
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- H + H He +n + energy
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- Part II Nuclear Energy
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- Mass Energy Equivalence Special Relativity
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- Nuclear Energy used to make Electricity 16% of the world's electricity is produced from nuclear energy. In the US 20% of electricity is made by about 130 nuclear reactor sites.
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- Nuclear Reactor at Indian Point, NY
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- Main Parts of a Nuclear Reactor Fuel Rods Neutron Moderator Control rods Coolant Containment
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- Fuel Rods Pellets of uranium oxide arranged in tubes in the reactor core. (Plutonium is also sometimes used as fuel). About 260 fuel rods form an assembly.
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- Neutron Moderator Slows down the neutrons released from fission so that they are captured by the fuel to continue the chain reaction. Water or graphite.
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- Control Rods Neutron-absorbing material such as cadmium, hafnium or boron, and are inserted or withdrawn from the core to control the rate of reaction, or to halt it.
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- Coolant A liquid or gas circulating through the core so as to transfer the heat from it.
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- Steam Generator The heat from the reactor is used to make steam to run the turbine to generate electricity.
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- Containment A one meter thick concrete and steel structure around the reactor core. Protects the core. Protects the environment from radiation in case of malfunction.
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- Refueling Every 1-2 years fuel rods are replaced. Spent fuel rods are still radioactive (nuclear waste).
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- Nuclear Reactors
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- Part III Detecting radiation
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- The Geiger Counter Radiation detector Hans Geiger
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- Operation of Geiger Counter The radiation ionizes a gas (argon) and frees electrons. The electrons are attracted to the positive electrode, that ionize gas again etc, producing a current pulse. This is amplified and heard as a sound.
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- Units of Radiation measured in rads (radiation absorbed dose), a unit of absorbed energy 1 rad = 0.01 joule of radiant energy absorbed/kilogram of tissue 1 rem (roentgen equivalent man) is the radiation dosage based on potential damage
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- Cosmic Rays Cosmic rays are of two types: high-energy particles. high-frequency electromagnetic radiation (gamma rays). They affect us indirectly by transforming nitrogen atoms in the air to radioactive carbon-14, which ends up in plants we consume.
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