Characterization of High Temperature Mechanical Properties for Lithium Metatitanate Pebble Beds

Lithium metatitanate (Li₂TiO₃) is a candidate tritium breeding material for fusion reactor blankets. In an actual blanket the pebbles are geometrically confined in a containing structure subjected to displacement and stress constraints under operating conditions. For an accurate description of pebble behavior during operations, existing data of pebble deformation under compressive loads is inadequate. In this study a uniaxial compression experimental apparatus was built to investigate time dependent creep on a single pebble as a function of applied force and temperature relevant to blanket conditions. Experimental results shows that at a temperature range of 700-800 °C, the crush load of Li₂TiO₃ pebbles is reduced by about half of its room temperature crush load. The experimental results allow for the establishment of a pebble creep failure map as a function of force and temperature, which provides guidance to the blanket designs. The study also introduces an FEA model based on experimental deformation data to obtain the constitutive equation needed for Discrete Element Model simulation of the pebble bed.