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

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Ends of the Nuclear Fuel Cycle
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The Reactor Core of the Nuclear Fuel Cycle
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The Nuclear Fuel Cycle
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Uranium Mining and Milling
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Yellow Cake
Final Product of Milling Step 70 to 80
uranium
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Conversion, Enrichment and Fuel Fabrication
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Natural Uranium
235U only fissile nuclide only 1 atom of 235U
in 140 atoms of 238U
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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

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Enrichment UF6 Feed Container
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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

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Enrichment Centrifuge Process
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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

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Enrichment Gaseous Diffusion Process
The large Tricastin enrichment plant in France
(beyond cooling towers). The nuclear reactors in
the foreground provide power for it.
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Conversion, Enrichment and Fuel Fabrication
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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

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UO2, Pellets and Fuel Assembly
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Fuel Rods
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Fuel Assembly
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MOX Fuel
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MOX Fuel
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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

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