Measurement of effective thermal conductivity of lithium metatitanate pebble beds by steady-state radial heat flow method

Abstract As a functional material of the tritium breeding blankets of the future fusion reactor, different candidates of the lithium-based ceramics have been considered to generate and release tritium. These tritium breeding materials in the form of packed pebble beds of nearly spherical-shaped particles have many advantages over the sintered pellets or blocks. For the design and analysis of the breeding blanket, the effective thermal conductivity (keff) of lithium-based ceramic pebble beds are required to be well characterized under the fusion-relevant conditions. In this study, an experimental setup has been fabricated and installed to estimate the keff of pebble beds as a function of bed temperature and filling gas pressure. The working principle of the experiment is based on the steady-state radial heat flow method. The various experiments have been performed on lithium metatitanate (Li2TiO3) pebbles having a diameter of 1 ± 0.15 mm to measure keff in the temperature range from 400 °C to 800 °C and in the environments of stagnant helium gas. The pressure of helium gas was adjusted from 0.105 MPa to 0.4 MPa (abs.) to account the effect of helium gas pressure. The increase in keff has been found with increasing the bed temperature and also increasing the helium gas pressure. The obtained results have been found comparable with the literature results with minimum difference.