In-pile irradiation induced defects and the effect on thermal diffusivity of MgO

The effects of neutron irradiation temperature and dose on thermal diffusivity are investigated by comparing non-irradiated and in-pile irradiated MgO samples. MgO pellets were irradiated in-pile of the Advanced Test Reactor at Idaho National Laboratory. Samples were irradiated at 623 and 973 K to fast neutron fluences of ∼1 × 1025 (1.5 dpa) and ∼2 × 1025 n/m2 (3 dpa). Post irradiation examination included X-ray diffraction, scanning electron microscopy, laser flash thermal diffusivity, and transmission electron microscopy. Neutron irradiation of MgO causes a significant reduction in the thermal diffusivity (46%–72% at room temperature) due to irradiation-induced defects. The radiation induced thermophysical and structural evolution of MgO is reported.