Neutron Diffraction Study of Radiation Damage in U3Si at 30°C and 350°C

We compare damage evolution in U3Si produced by neutron irradiation at 30°C and 350°C and measured by neutron diffraction. Initial studies found that increasing neutron irradiation dose at 30°C results in monotonic expansion of the a-axis and contraction of the c-axis that transforms the crystal structure from tetragonal to cubic [1]. Additional irradiation results in amorphization. Neutron irradiation at 350°C results in little change to the a-axis and expansion of the caxis.The complete alteration in lattice dilatation during irradiation is interpreted as due to modification of surviving defect configurations at the higher temperature. The high temperature lattice dilations can be explained by defect loop formation in the a-b plane. Confinement of lattice strain to the c-axis during irradiation at 350°C may be the mechanism that prevents the total lattice dilatation from exceeding the critical level required for amorphization.