Nuclear Fuel, Uranium Enrichment, Fuel Fabrication, MOX - PowerPoint PPT Presentation

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Nuclear Fuel, Uranium Enrichment, Fuel Fabrication, MOX

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Title: Nuclear Fuel, Uranium Enrichment, Fuel Fabrication, MOX


1
Nuclear Fuel, Uranium Enrichment, Fuel
Fabrication, MOX
  • Seminar on
  • Nuclear Science and Technology
  • for Diplomats
  • P. Adelfang
  • ()Division of Nuclear Fuel Cycle and Waste
    Technology (NEFW)
  • Department of Nuclear Energy (NE)
  • IAEA, Vienna, February 6-8, 2007

2
Ends of the Nuclear Fuel Cycle
3
The Reactor Core of the Nuclear Fuel Cycle
4
The Nuclear Fuel Cycle
5
Uranium Mining and Milling
6
Yellow Cake
Final Product of Milling Step 70 to 80
uranium
7
Conversion, Enrichment and Fuel Fabrication
8
Natural Uranium
235U only fissile nuclide only 1 atom of 235U
in 140 atoms of 238U
9
Enrichment
  • A number of enrichment processes have been
    demonstrated in the laboratory
  • Only two, the gaseous diffusion process and the
    centrifuge process, are operating on a commercial
    scale
  • In both of these, UF6 gas is used as the feed
    material
  • Molecules of UF6 with U-235 atoms are about one
    percent lighter than the rest, and this
    difference in mass is the basis of both processes
  • Large commercial enrichment plants are in
    operation in France, Germany, Netherlands, UK,
    USA, and Russia, with smaller plants elsewhere

10
Enrichment UF6 Feed Container
11
Enrichment Centrifuge Process
  • vacuum tubes, each containing a rotor one to two
    metres long and 15-20 cm diameter.
  • rotors are spun rapidly, at 50,000 to 70,000 rpm
  • heavier molecules with U-238 increase in
    concentration towards the cylinder's outer wall
  • there is a corresponding increase in
    concentration of U-235 molecules near the centre.
  • enriched gas forms part of the feed for the next
    stages, depleted UF6 gas goes back to the
    previous stage (cascade)
  • very high speeds, outer wall spinning cylinder
    400 and 500 metres per second 1 million times
    the acceleration of gravity

12
Enrichment Centrifuge Process
13
Enrichment Gaseous Diffusion Process
  • involves forcing UF6 under pressure through a
    porous membranes
  • as 235U molecules are lighter than the 238U
    molecules they move faster and have a slightly
    better chance of passing through the pores in the
    membrane
  • the UF6 which diffuses through the membrane is
    thus slightly enriched, while the gas which did
    not pass through is depleted in 235U
  • this process is repeated many times in a series
    of diffusion stages called a cascade
  • enriched UF6 is withdrawn from one end of the
    cascade and depleted UF6 is removed at the other
    end
  • the gas must be processed through some 1400
    stages to obtain a product with a concentration
    of 3 to 4 235U

14
Enrichment Gaseous Diffusion Process
The large Tricastin enrichment plant in France
(beyond cooling towers). The nuclear reactors in
the foreground provide power for it.
15
Conversion, Enrichment and Fuel Fabrication
16
Conversion and Nuclear Fuel Fabrication
  • UF6, in solid form in containers, is heated to
    gaseous form, and the UF6 gas is chemically
    processed to form LEU uranium dioxide (UO2)
    powder
  • this powder is then pressed into pellets,
    sintered into ceramic form (fuel pellets)
  • pellets are then loaded into Zircaloy tubes that
    are afterwards hermetically closed (fuel rods)
  • rods are constructed into fuel assemblies
  • fuel assemblies are made with different
    dimensions and number of fuel rods, depending on
    the type reactor

17
UO2, Pellets and Fuel Assembly
18
Fuel Rods
19
Fuel Assembly
20
MOX Fuel
21
MOX Fuel
22
MOX Fuel
  • Plutonium, made in power reactors and from
    dismantled nuclear weapons, is a valuable energy
    source when integrated in the nuclear fuel cycle
  • Over one third of the energy produced in most
    nuclear power plants comes from plutonium. It is
    created there as a by-product.
  • 'MOX' is derived from 'mixed oxides', and refers
    to reactor fuel made from a mixture of plutonium
    and uranium oxide
  • For use in a light water reactor, the proportion
    of plutonium is about 5. This is a similar
    fissile content as low enriched uranium fuel
  • MOX is formed into ceramic fuel pellets,
    extremely stable and durable, and which are
    sealed in metal (usually zirconium) tubes, which
    in turn are assembled into fuel elements
  • In most cases a part of the reactor core can be
    loaded with MOX fuel elements without engineering
    or operational modifications to the reactor
  • Plutonium is radiologically hazardous,
    particularly if inhaled, so must be handled with
    appropriate precautions

23
MOX Fuel Glove Boxes
24
MOX Fuel Glove Boxes
25
IAEA
Thank you for your attention
atoms for peace.
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