Effect of Additives on Irradiation-Induced Change of Lattice Parameter in ThO₂

Abstract

Irradiation-induced change of the lattice parameter in ThO₂ doped with small amounts of CaO, Y₂O₃ or Nb₂O₅ was investigated in the fission dose to 2.5×10²³ fissions-m⁻³. The fission dose dependence of the lattice growth was well approximated by a simple exponential model, suggesting that irradiation-induced interstitials exist stably at low fission doses. On the other hand, the lattice growth was found to be enhanced by doping, though no clear difference between dopants was observed. A mutual relationship between irradiation-induced lattice growth and lattice defects generated by irradiation and by doping was examined. Also, a simple model was proposed to explain the effect of grain size on the irradiation-induced lattice growth.

KEYWORDS:

• nuclear fuels
• thorium oxides
• lattice parameter
• fission dose
• interstitials
• vacancy
• grain size
• grain growth
• point defects
• irradiation
• radiation effects
• additives