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The Nuclear Fuel Cycle

The Nuclear Fuel Cycle. Dr. Okan Zabunoğlu Hacettepe University Department of Nuclear Engineering. 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) .

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The Nuclear Fuel Cycle

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  1. The Nuclear Fuel Cycle Dr. Okan Zabunoğlu 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) Fabrication (produce fuel elements and assemblies) Enrichment 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 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 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

  5. The Standard Reprocessing PUREX: Solvent extraction with tri-butyl phosphate Co-decontamination of U+Pu 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.

  7. Alternative Reprocessing Schemes • Modified Purex Partial co-processing (Products: U+Pu and U) Complete co-processing (Product: U+Pu) 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).

  8. 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.

  9. 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

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