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Nuclear Reactions

Nuclear Reactions. Chemistry Mrs. Coyle. Part I. Fission and Fusion. Transmutations. When a nucleus of an element is transformed to a nucleus of another element. Transmutations. Can occur through: Decay (Spontaneously) Nuclear Reactions (Fusion and Fission). Nuclear Reactions. Fission

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Nuclear Reactions

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  1. Nuclear Reactions ChemistryMrs. Coyle

  2. Part I • Fission and Fusion

  3. Transmutations • When a nucleus of an element is transformed to a nucleus of another element.

  4. Transmutations • Can occur through: • Decay (Spontaneously) • Nuclear Reactions (Fusion and Fission)

  5. Nuclear Reactions • Fission • Fusion

  6. Nuclear Fission • Enrico Fermi (USA) 1930’s • Lise Meitner, Strassman, Hahn (Germany) • Bombarding neutrons at 235U or 239Pu 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

  7. Nuclear Fission Chain Reaction Neutron bombardment n + 235U  236U X+Y +n + energy

  8. Nuclear Fission • 235U is a rather rare isotope(0.7%) of the more abundant 238U which does not undergo fission. • Nuclear Bomb • Nuclear Power Plants

  9. Nuclear Fusion • Sun’s energy comes from fusing of hydrogen to form helium • Product has higher mass number than reactant

  10. H + H  He +n + energy

  11. Part II • Nuclear Energy

  12. E=mc • Mass – Energy Equivalence • Special Relativity

  13. 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.

  14. Nuclear Reactor at Indian Point, NY

  15. Main Parts of a Nuclear Reactor • Fuel Rods • Neutron Moderator • Control rods • Coolant • Containment

  16. 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.

  17. 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.

  18. Control Rods • Neutron-absorbing material such as cadmium, hafnium or boron, and are inserted or withdrawn from the core to control the rate of reaction, or to halt it.

  19. Coolant • A liquid or gas circulating through the core so as to transfer the heat from it.

  20. Steam Generator • The heat from the reactor is used to make steam to run the turbine to generate electricity.

  21. 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.

  22. Refueling • Every 1-2 years fuel rods are replaced. • Spent fuel rods are still radioactive (nuclear waste).

  23. Nuclear Reactors

  24. Part III • Detecting radiation

  25. The Geiger Counter • Radiation detector • Hans Geiger

  26. 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.

  27. 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

  28. 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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