核分裂片照射による酸化トリウム燃料核の格子定数変化に及ぼす結晶粒径の影響

概要

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The polished hemispheres of ThO2 kernels were irradiated by fission fragments, which recoiled from the covered Al-U alloy foils. After irradiation, the lattice parameters of the kernels were measured by micro-beam X-ray diffractometer. It was found that the lattice parameter increased with increasing fission fragment dose and reached a saturation value at doses higher than about 5×1016 fission fragments-cm-3. With increasing grain sizes from 4.0 to 19.3 μm, the saturation values of lattice parameter changes increased from approximately 0.07 to 0.18%. The recovery began at about 400°C in all specimens and the temperature of the complete recovery had a tendency to become higher with increasing grain size. These results lead to a conclusion that the grain boundaries act as a sink of the defects created by fission fragments.