The Nuclear Fuel Cycle

1
The Nuclear Fuel Cycle

• Dr. Okan Zabunoglu
• Hacettepe University
• Department of Nuclear Engineering

2
Front End of the NFC (before the reactor)
Uranium in Nature Exploration Mining (remove
ores) Milling (concentrate ores)
Refining (purify and convert to uranium
hexafluoride)
Enrichment
Fabrication (produce fuel elements and assemblies)
Nuclear Reactor (LWR)
3
Back End of the NFC (after the reactor)
Temporary storage of spent fuel (in pool, on-site)
LWR
Reprocessing (recovery of valuable materials)
Off-site storage Preparation Packaging
HLW
Recovered products
Final disposal of SF
Solidification Preparation Final disposal of HLW
Reuse
4
Fresh and Spent LWR Fuels
A 1000-MWe LWR thermal efficiency
0.325 exposure time 1100 days capacity factor
0.80 burnup 33000 MWd/ton
Fresh Fuel 27 tons U per yr
Spent Fuel 27 tons per yr

• U-235 3.3 w/o
  U 95.5 w/o
• U-238 96.7 w/o
  U-235 0.83 w/o
• 
  Pu 0.9 w/o
• 
  Fissile
  Pu 70 w/o
• 
  FPs 3.5 w/o
• 
  Other
  Actinides 0.1 w/o

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• The Standard Reprocessing
• PUREX Solvent extraction with tri-butyl
  phosphate
• Co-decontamination of UPu from FPs
  (producing a HLW solution) and partitioning of
  U and Pu.
• Products a pure U and a pure Pu solution.
  
• Recovered U (sufficiently decontaminated from
  fission products to be handled by
  direct-contact) Enrich and fabricate.
• Recovered Pu (highly pure) Blend it with a
  fertile makeup (depleted U, natural U, or
  recovered U from reprocessing) to adjust its
  fissile content and fabricate into mixed-oxide
  (MOX) fuel.

6
Requirements in a civilized LWR cycle

• Contradiction Plutonium product of
  reprocessing is to be blended with a fertile
  makeup (depleted, natural, or recovered U) before
  being loaded into a reactor. Then, why in the
  first place separate Pu in a highly pure form?!
• It is not necessary to produce pure Pu in
  reprocessing. About 93-95 U in Pu is an
  appropriate fraction
• for MOX fuel.
• In addition, since Pu has an inherent beta (and
  gamma) activity, it is not required to
  decontaminate Pu from the fission products by a
  great extent.

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Alternative Reprocessing Schemes

• Modified Purex
• Partial co-processing (Products UPu and U)
• Complete co-processing (Product UPu)
• Several options regarding separation of
  other actinides
• (Np, Am, Cm) and certain fission
  products
• DUPIC (Direct Use of spent PWR fuel in CANDU
  reactors) Direct fabrication of CANDU fuel from
  spent PWR fuel materials by thermal and
  mechanical processes (no aqueous processing like
  in Purex).

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• Pyro-processing Pyrometallurgical and
  pyrochemical (electrorefining) processing to
  obtain (1) pure U, (2) Pu and other actinides
  (together with some U), and (3) fission products.
• Originally planned to be part of the IFR
  (Integral Fast Reactor) concept.
• Spent LWR fuels can also be pyroprocessed after
  an initial reduction-to-metal step, leading to a
  combined IFR-LWR system.
• In any case, Pu and other actinides recovered by
  pyroprocessing can be burned in a fast-neutron
  spectrum, thus leaving fission-products waste
  only.

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Concluding remarks

• Whether or not to close the nuclear fuel cycle
  and how to close it...
• Burdens of the standard reprocessing
• economic uncertainties
• safeguardability considerations
• Utilization of resources
• Effects on waste disposal