Radiation changes in the nanostructure of graphite-like boron nitride and monitoring of the temperature of in-channel reactor irradiation

Abstract

Graphite-like materials, due to the strong anisotropy of the crystal structure, are microscopically different-modular, i.e. they have significantly different elastic resistance to tension and compression at the subatomic level. As a result of microscopically different-modular the crystallite microdeformations unavoidable in ceramic materials cause large shifts and non-uniform broadening of X-ray lines. Reactor irradiation changes both the magnitude of microdeformations and the microscopic different-modular of graphite-like nano-structured materials. The microscopic different-modular of boron nitride ceramics is analyzed by X-ray line decomposition (00l) using Lorentz functions. In pyrolitic materials (very microscopically different-modular materials) it is necessary to use approximation by Poisson distribution of X-ray lines rearranged in dimensionless coordinates (00l). A method for determining temperature during high dose (up to 3∙1023 n/cm2) high-temperature (up to 1800 K) reactor irradiation of material science containers using pyrolytic boron nitride monitors is described. The method uses the relationship between the magnitude of induced microscopic different-modular of the material and the irradiation temperature.