Rim structure formation of isothermally irradiated UO2 fuel discs

K. Une, K. Nogita, T. Shiratori, K. Hayashi

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27 Citations (Scopus)


UO2 fuel discs, which had been irradiated at an isothermal condition of 550-630 °C to 51, 86 and 90 GWd/t without any restraint pressure, have been subjected to detailed microstructure observations, elemental analyses and density measurements. Their data were compared with previously reported results of high-burnup Zircaloy-clad type fuel pellets, so as to clarify the effect of pellet-cladding interaction (PCI) restraint on the rim structure formation. The porous rim structure, accompanying huge bubbles and high porosity, was recognized for the high-burnup discs of 86 and 90 GWd/t, but not for the 51 GWd/t disc. From the good coincidence between porosity increase and density decrease for the high-burnup discs, it was concluded that the precipitation and growth of coarsened rim bubbles substantially caused fuel swelling. The wide variety of rim bubble sizes and porosities at a given local burnup, which was recognized in the present PCI-free discs and Zircaloy-clad type pellets reported in other literature, possibly resulted from the external PCI restraint effect. The pressure difference between bubble internal and external pressures, and vacancy diffusivity would rate-control the growth of rim bubbles.

Original languageEnglish
Pages (from-to)20-28
Number of pages9
JournalJournal of Nuclear Materials
Issue number1
Publication statusPublished - Jan 2001

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Materials Science(all)
  • Nuclear Energy and Engineering


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