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Nuclear Power Plants

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Title: Nuclear Power Plants


1
Nuclear Power Plants
  • A Brief Overview

2
What We Use Them For
  • Most Significant Current Use
  • Nuclear Power (Generation of Electrical Power)
  • Others Uses
  • Nuclear Propulsion (in devices such as rockets)
  • Transmutation of Elements (production/creation of
    Plutonium/other radioactive isotopes for uses
    such as radiation therapy)
  • Research/Technology (neutron and positron
    radiation)

3
Nuclear Power Plants Around The World
4
Map of Site
5
Nuclear Reactor Designs
  • Thermal (slow) Reactors
  • Use slow neutrons b/c they have higher
    probability of fissioning U-235
  • Have moderator, fuel, containments, pressure
    vessels, shielding, instrumentation to
    monitor/control systems of reactor
  • Three Types
  • pressurized fuel channels, large pressure
    vessel, gas cooling
  • Fast Reactors
  • Use fast neutrons to sustain chain reaction
  • Do not have moderating material
  • Require heavily enriched fuel/ Plutonium to
    reduce amount of U-238 that would normally absorb
    fast neatrons

6
Various Types of Nuclear Reactors
  • Pool-type Reactor
  • Pressurized Water Reactor
  • Boiling Water Reactor
  • Fast Breeder Reactor
  • Pressurized Heavy Water Reactor
  • Magnox Reactor
  • Advanced Gas-Cooled Reactor
  • Light-Water Cooled Graphite Moderated Reactor
    (RBMK)
  • Aqueous Homogenous Reactor
  • Liquid Fluoride Reactor

7
The General Nuclear Fuel Cycle
  • NUCLEAR FISSION
  • Heavy Atom? Splits?Total Mass of Smaller
    Productslt Mass of Original Atom
  • Where is the mass that is unaccounted for?
  • Einsteins EMC2
  • mass difference ? converted to ? energy

8
Nuclear Fission
9
Nuclear Fission in Reactors and Generation of
Electricity
  • Fuel (type of Uranium or sometimes Plutonium)
  • Nuclear fission occurs when a heavy nucleus is
    struck by a neutron and is divided into two
    smaller nucleuses as well as extra neutron
  • This starts the chain reaction of nuclear fission
    and is the basis for nuclear energy

10
Nuclear Fission (Cont.)
  • If the stable atom of Uranium-235 is converted to
    the unstable U-236 by adding a neutron, it
    immediately begins to decay by splitting into
    smaller atoms and it releases energy.
  • Chain Reaction
  • Each time an atom breaks apart and gives off
    neutrons, those neutrons fly into other U-235
    atoms and cause them to decay
  • Most neutrons move too quickly and simply bounce
    off the heavier atoms, so a coolant is introduced
    to slow them down and continue the chain reaction

11
Chernobyl Nuclear Power Station When, Where, and
Why Was it Built?
http//video.google.com/videoplay?docid-401766423
4059701260qchaes
12
V.I. Lenin Memorial Chernobyl Nuclear Power
Station
  • Located in Prypiat, Ukraine, 18 kilometers
    Northwest of Chernobyl, very lose to border of
    Ukraine/Belarus
  • Increase in electricity demand? generation of new
    power plants
  • Construction began in 1970s
  • Four Reactors up and running by 1986

13
The Specifics Chernobyls Reactor Design, the
Meltdown, and Why it Occurred
14
The Reactors
  • Four RBMK-1000 reactors in use that each produced
    1 GW of electric power, Two more under
    construction
  • RBMK-1000 Reactor Design
  • reaktor bolshoy moshchnosti kanalniy
  • Type of graphite-moderated nuclear power reactor
  • Built only in Soviet Union

15
RBMK-1000 Design
16
What Makes the RBMK Reactor Unlike ANY Other
Fission Reactor?
  • It uses neutron-absorbing light water (as
    opposed to hard water for cooling and fixed
    graphite for moderating (combination of graphite
    moderator and water coolant is not found in any
    other reactors)
  • Based on design intended to produce plutonium
    (for weapons)
  • Ability to refuel without shutting down reactor
  • Positive void coefficient
  • Can use natural Uranium for fuel as opposed to
    enriched Uranium
  • These factors make a large reactor possible,
    however, they also make it very unstable,
    especially at low power levels

17
RBMK Reactor How it Functions
  • Powered by slightly enriched uranium dioxide fuel
    pellets (U-235)
  • Uses solid graphite to slow down neutrons
  • Fuel rods arranged cylindrically to form fuel
    assembly, and two fuel assemblies are stacked on
    top of each other and placed in individual
    pressure tubes (allows reactor to be refueled
    while running)
  • Graphite blocks between pressure tubes act as
    moderators

18
RBMK Reactor How it Functions (Cont.)
  • Boron Carbide Control Rods control reaction
  • Water is pumped through each pressure tube,
    allowed to boil, and drives the turbines

19
The Meltdown
  • What Happened?

20
  • Reactor Number 4 was scheduled to be shut down
    for maintenance which gave rise to
  • Opportunity to test ability of reactors turbine
    to generate enough electricity to power reactors
    safety systems in case outside electric power was
    lost
  • AIM/ GOAL OF TEST ? TO DETERMINE WHETHER THE
    TURBINES IN THE RUNDOWN PHASE COULD POWER PUMPS
    WHILE GENERATORS WERE STARTING UP
  • Test not able to be carried out during day, so it
    was left for underqualified night crew

21
  • Electricity to water pumps shut off
  • ? Water flow rate decreased
  • 2. Turbine disconnected from reactor
  • ?Increased level of steam in reactor core
  • Coolant heated, steam formed voids in coolant
    lines
  • ?Power of Reactor Increased Rapidly
  • All control rods fully inserted to shutdown the
    reactor
  • ?Slow speed of control rod insertion mechanism
    caused reaction rate to increase
  • ?Deformation of Control Rod Channels
  • ? Control Rods stuck, reaction unable to be
    stopped

22
5. Fuel Rods melted, steam pressure
increased ?HUGE steam explosion 6. Steam
travelled up control rod channels ?displaced and
destroyed reactor lied, ruptured tubes, blew
HOLE in roof 7. Oxygen rushing in high
temperature of reactor fuel and graphite
moderator ?graphite fire
23
A Scram
  • In an emergency, a set of control rods that can
    be inserted into the core to absorb the neutrons
    are dropped to stop the reaction completely
  • Coolant is circulated around core to extract heat
    and becomes highly radioactive
  • In the RBMK reactor, the primary coolant is
    boiled within the reactor to produce steam
    directly
  • Assembly housed in concrete containment building
    (only PARTIAL containment)

24
WHY?
25
  • Design Theory (Flaws in Design)
  • Large positive void coefficient (produces more
    energy as it gets hotter, unlike most reactor
    designs which are exact opposite)
  • Graphite tipped control rods (at time of initial
    insertion, graphite ends displace coolant, which
    greatly increases rate of fission reaction)
  • Temperature gradient in core (uneven temperature
    distribution, not all parts of core temp, being
    evenly moderated)
  • Only Partial Containment

26
  • Operator Theory
  • Operators careless and violated plant procedures
  • Operators not informed by designers of dangerous
    conditions for reactor
  • Operators lacked proper experience/training
    (Non-RBMK-qualified personnel on duty at time of
    test)
  • Insufficient communication between safety
    officers and operators (in charge of experiment
    being run that night)
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