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Merits and Viability of Different Nuclear Fuel Cycles and Technology Options and the Waste Aspects of Advanced Nuclear Reactors (2023) / Chapter Skim
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Appendix G: Reprocessing and Geologic Disposal of TRISO Fuel
Pages 289-294

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From page 289...
... . Initial work in TRISO fuel processing involved burning the outer layers of graphite and then crushing the fuel particles using steel rollers to expose the fuel for dissolution in nitric acid, followed by processing using the standard PUREX flow sheet (IAEA, 2008)
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From page 290...
... Remaining challenges for TRISO fuel reprocessing include handling the volatile fission products in the off-gas, improving the recovery efficiencies, and scaling up all steps of the process. Nitric acid leaching can leave solid residues, such as undissolved noble metals, SiC shell fragments, SiO2, and NaSiO3-containing residues, which can lead to the formation of silicic acid and complicate subsequent separation steps (Del Cul et al., 2002)
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From page 291...
... Furthermore, the retention of radionuclides appeared to be inversely proportional to void size. Direct Disposal of TRISO in a Geologic Repository There have been many studies relevant to the direct disposal of very-high-temperature TRISO fuels in a geologic repository, with most analyses examining the properties and performance of the graphite matrix and SiC coating within a geologic disposal environment.
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From page 292...
... intact fuel kernel particles retain fission products nearly completely, and (2) releases from defective or failed particles and from the matrix sphere are rapid, but the contribution to released radioactivity is small.
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From page 293...
... , on the other hand, may damage fuel particles and cause the release of fission products. Future Research Needs for TRISO Fuel Despite the significant research efforts on TRISO fuel properties described above, additional research is required to better understand the behavior of TRISO fuel under irradiation and in a repository environment, as well as to improve methods for processing spent TRISO fuel and managing radioactive graphite wastes.
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From page 294...
... . There have been proposals for the importance of the graphite matrix in reducing the release of radionuclides from TRISO fuels; however, before one can claim credit for this barrier function, there is a need for detailed materials studies of the mechanisms of graphite corrosion in repository environments (van den Akker and Ahn, 2013)
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Key Terms

  • graphite matrix
  • spent triso
  • geologic repository
  • fuel kernels
  • sic layers

  • sic layer
  • del cul
  • direct disposal
  • fuel particles
  • triso particles

  • triso fuels
  • fuel kernel
  • nuclear fuel
  • fuel elements
  • fission products

  • sic shell
  • radiation damage
  • spent fuel
  • advanced fuel
  • waste form

  • nitric acid
  • fission product
  • fuel reprocessing
  • fuel form
  • fuel forms

  • sic coating
  • estimated time
  • barrier function
  • alpha decay
  • nitrate salt


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