Measurement of effective thermal conductivity of lithium metatitanate pebble bed by transient hot-wire technique

Abstract

Abstract In future fusion reactor lithium metatitanate (Li2TiO3) as a functional material in the form of packed pebble beds have been selected in breeding blanket concepts to generate and release tritium. The effective thermal conductivity (keff) of Li2TiO3 pebble beds are needed to be well characterized for the design and analysis of breeding blankets under fusion relevant conditions. The transient hot-wire technique based experimental system has been fabricated, tested and installed for keff measurement of Li2TiO3 pebble beds. Finite element method (FEM) simulations have been performed to optimize the dimension of an experimental setup with the intention of minimizing the uncertainty in keff measurements. The experiments have been performed on 1 ± 0.15 mm diameter Li2TiO3 pebble bed with a packing fraction of 63 %. The influences of temperature (35–800 °C), gas environment (helium and air) and gas pressure (0.105−0.4 MPa (abs.)) have been investigated on keff of Li2TiO3 pebble beds. Reduction in keff was found with a decrease in helium gas pressure while the reduction in keff was not significant with a decrease in air pressure. The measured keff results of Li2TiO3 pebble beds have been compared and agreed well with the literature experimental results. The empirical correlations are also proposed for keff of Li2TiO3 pebble beds in helium and in air environment at 0.105−0.4 MPa and as a function of temperature.