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LECTURE 9 NUCLEAR POWER GENERATION

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LECTURE 9NUCLEAR POWER GENERATION. ECE 371. Sustainable Energy Systems. Dr. Rostamkolai – PowerPoint PPT presentation

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Title: LECTURE 9 NUCLEAR POWER GENERATION


1
LECTURE 9NUCLEAR POWER GENERATION
Dr. Rostamkolai
  • ECE 371
  • Sustainable Energy Systems

2
INTRODUCTION
  • If the current coal usage continues, the coal
    supply in the world will be depleted in 155 years
  • Nuclear energy as it is known today was
    highlighted by Einstein in 1905
  • E mc2

3
INTRODUCTION
  • Theoretical research in controlled fission
    resulted in the first successful demonstration of
    a self-sustained chain reaction at the University
    of Chicago in 1942 as a part of the Manhattan
    Project
  • Nuclear power plants were first developed for
    naval propulsion and energy production in 1950s
    (higher-specific-energy fuels)

4
INTRODUCTION
  • Expansion in US halted in 1970s
  • Overbuilt generation
  • Reduction in load growth
  • Most nuclear plants are light water reactors
  • Pressurized Water Reactor (PWR) Most Common
  • Boiling Water Reactor (BWR)

5
PWR
  • 2300 psi, 315oC

6
BWR
  • 1000 psi, 285oC

7
HISTORICAL PERSPECTIVE
  • The worlds first nuclear-powered electric
    generating plant was constructed by Soviet Union
    in 1954 5 MW
  • The first US PWR was constructed and placed in
    service by Westinghouse at Pennsylvania in 1957
  • The first US BWR was constructed and placed in
    service by GE at California in 1957 5 MW

8
HISTORICAL PERSPECTIVE
  • The following figure shows the number of nuclear
    plant orders placed annually

1973 Arab Oil Embargo
1979 Three Mile Island 2
9
INTRODUCTION
10
HISTORICAL PERSPECTIVE
  • There are 439 nuclear plants in the world, with
    104 of them in 31 US states

11
HISTORICAL PERSPECTIVE
12
HISTORICAL PERSPECTIVE
13
BACKGROUND
  • Nuclear energy is obtained from the atom nuclei
    through a controlled reaction
  • The possibility of harvesting the nuclear energy
    was first recognized in the 1930s and early 1940s
  • The idea of obtaining large amounts of energy
    from small amounts of material was very exciting
    to the scientists

14
BACKGROUND
  • An elements chemical nature is determined by the
    number of electrons in its atom
  • In a neutral atom, the number of electrons is
    equal to the number of protons in the nucleus
  • The positive charge of protons are cancelled by
    the negative charge of electrons

15
BACKGROUND
Radioactive
16
BACKGROUND

Mass Number (Number of Protons)
(Number of Neutrons)
17
BACKGROUND
  • The number of protons in a nucleus determines the
    elements
  • The number of neutrons determines the isotope
  • Example
  • Uranium nucleus has 92 protons
  • If it has 143 neutrons, it is Uranium-235
  • If it has 146 neutrons, it is Uranium-238

18
BACKGROUND
  • There are 14 known isotopes of uranium
  • Approximately 1000 distinct isotopes have been
    identified experimentally
  • They are grouped into 103 elements with names
  • There are 4 more elements shown in charts, but
    two are un-named

19
BACKGROUND
  • Of all identified isotopes, 279 of them are
    stable
  • They are nuclei that do not experience natural
    decay (disintegration)
  • The rest have some intrinsic nuclear imbalance
    which eventually causes them to change their
    structure
  • Such changes always lead to a more stable isotope
    and involve the emission of some disintegration
    product

20
BACKGROUND
  • The emitted particles are
  • Electron beta decay
  • Helium nuclei alpha decay
  • All nuclei, except hydrogen H1, can be excited
    without altering its basic nuclear structure
  • They eventually return to their natural state by
    emitting one or more protons

21
BACKGROUND
  • These protons are very high energy and called
    gamma rays
  • Nuclei can be excited artificially by bombarding
    them with
  • Photons
  • Neutron
  • Helium nuclei

22
BACKGROUND
  • Nuclei can also have their isotopic
    identification changed by bombardment and capture
  • These changes are called isotopic transmutation
    and play a central role in the physics of nuclear
    reactors

23
BACKGROUND
  • A chemical reaction is a reaction which involves
    electrons
  • Nuclear reaction is a reaction which involves the
    nucleus of an atom
  • Nuclear reactions produce more energy per atom
    than chemical reactions

24
BACKGROUND
  • This is because nuclear forces holding the
    nucleus together are much stronger than the
    electrostatic forces that are holding electrons
  • The most commonly observed from a nuclear
    reaction is the radioactive decay
  • The radioactive decay causes a heavy atom to
    transform to a lighter atom of a different element

25
BACKGROUND
  • For example, in the following a radioactive decay
    of Uranium 238 decomposes it to Thorium with the
    release of an alpha particle (He nuclei)

26
NUCLEAR REACTION
  • It is a reaction that changes the number of
    protons or neutrons in the nucleus of an atom
  • There are several kinds of nuclear reactions
  • Fragmentation of large nuclei into smaller ones
  • Nuclear fission
  • Building up of small nuclei into larger ones
  • Nuclear fusion

27
NUCLEAR FISSION
  • It is a nuclear reaction in which nucleus of an
    atom splits into smaller parts
  • This process often release neutrons
  • Self-sustaining chain reaction, if slowed
    (concept of moderator invented by Fermi)
  • It also releases enormous amount of energy in the
    form of heat

28
NUCLEAR FISSION
  • In 1939 Hahn and Strassman in Berlin bombarded a
    Uranium-235 isotope with neutrons and
    demonstrated nuclear fission for the first time

Barium
Krypton
29
NUCLEAR FISSION
  • The naturally mined uranium contains 0.7 of
    U-235 and 99.3 of U-238
  • Separation is difficult
  • Bohr found that nuclear fission was much more
    likely to occur in Uranium-235 isotope than in
    Uranium-238
  • The process of enrichment was developed to
    increase concentration of U-235 in the mixture

30
NUCLEAR POWER PLANT
  • In a nuclear power plant, a nuclear reactor
    produces and controls the release of energy from
    splitting the atoms of elements such as uranium
    and plutonium
  • The energy released as heat from the continuous
    fission of the atoms in the fuel is used to make
    steam

31
NUCLEAR POWER PLANT
32
CORE
  • Reactor core is the portion of the nuclear
    reactor which contains the nuclear fuel where the
    nuclear reaction takes place
  • The main function of a core is to create an
    environment which establishes and maintains the
    nuclear chain reaction
  • It provides a means for controlling the neutron
    population and removing the energy released
    within the core

33
MODERATOR
  • Moderator is a material which slows down the
    released neutrons from the fission process
  • Slow moving neutrons are much more likely to be
    absorbed by uranium atoms to cause fission than
    fast moving neutrons
  • Newly released neutrons after a nuclear fission
    move at 300,000 km/sec

34
MODERATOR
  • It must be slowed down or moderated to speeds
    of a few km/sec
  • This is necessary to cause further fission and
    continue the chain reaction

35
MODERATOR
  • The most commonly moderators are
  • Water - H2O
  • Light water reactor
  • Not efficient it slows neutrons and also
    absorbs them
  • Heavy water D2O (formed by a heavier isotope of
    hydrogen with atomic mass 2)
  • Heavy water reactor
  • Efficient
  • Graphite

36
FUEL
  • The most common fuel is
  • Uranium-235
  • Plutonium-239
  • Light water reactors use uranium oxide (UO2)
    pellets which are arranged in zirconium alloy
    tubes to form fuel rods (melting point of UO2 is
    2800oC)

37
FUEL
  • Pellets are 1 cm in diameter and 1.5 cm long

38
FUEL
  • The fuel rods are placed in fuel assemblies in
    the reactor core

39
CONTROL ROD
  • It is made of neutron-absorbing material
  • Cadmium
  • Hafnium
  • Boron
  • Rods are used to control the rate of reaction
  • They are inserted or withdrawn from the core to
    decrease or increase the rate of fission

40
CONTROL ROD
41
CONTROL ROD
  • Inserting the rod slows down the reaction by
    absorbing the neutrons and reducing the available
    neutrons for fission
  • Withdrawing them has the opposite effect
  • Allowing the rate of fission to grow beyond a
    certain point can be very dangerous (Chernobyl)

42
COOLANT
  • It is a liquid or gas circulating around or
    through the core
  • It carries the heat away from the reactor
  • It generates steam in the steam generator
  • The most common coolant is pressurized water

43
STEAM GENERATOR
  • It is a heat exchanger
  • Uses heat from the core which is transported by
    the coolant
  • Produces steam for the turbine

44
CONTAINMENT
  • It is the structure around the reactor core
  • It protects the core from outside intrusion
  • Protects outside environment from effects of
    radiation in case of a malfunction
  • Typically it is a meter thick concrete and steel
    structure

45
SPENT FUEL POOL
  • It stores the spent fuel from the nuclear reactor
  • About 1/4 to 1/3 of the total fuel is removed
    from the core every 12 to 18 months and replaced
    with the fresh fuel
  • The removed fuel rods still generate a lot of
    heat and dangerous radiation

46
SPENT FUEL POOL
  • The fuel bundles freshly removed from the core
    are separated for several months for initial
    cooling
  • Then they are sorted in other parts of the pool
    for final disposal
  • Metal racks keep the fuel in safe positions to
    avoid the possibility of a nuclear chain reaction

47
SPENT FUEL POOL
  • The spent fuel is typically stored underwater for
    10 to 20 years before being sent for disposal or
    reprocessing

48
PRODUCTION COST OF NUCLEAR POWER
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