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Nuclear Reactions

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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. – PowerPoint PPT presentation

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Title: Nuclear Reactions


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) 1930s
  • 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 ?XY 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
  • Suns 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

Emc
  • 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    hafnium or boron, and are inserted or withdrawn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
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27
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.

28
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

29
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30
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31
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32
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.

33
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