Stress in alumina insulator due to irradiation

This paper reports on alumina (Al2O3), a traditional high temperature electrical insulator, which is known to undergo shape changes during neutron irradiation as a result of its basic anisotropic hexagonal crystal structure. The mechanical stability of this insulating material is critical for its proper utilization for thermionic reactors. A theoretical model based on experimental data was established to predict the stress induced by fast neutron irradiation in alumina at high temperatures. This model can be divided into three portions: the generation of stress due to anisotropic growth of individual grains, the reduction of the induced stress by spontaneous relaxation of the elastic medium and the reduction of stress by long term creep. The dependence of stress profile on temperature, neutron flux, creep rate, elasticity constants and micro-anisotropy was determined under irradiation conditions encountered in thermionic reactors. The lifetime of the material was predicted based on the governing equations and the critical material parameters