Size dependent crush analysis of lithium orthosilicate pebbles

TL;DR

This study investigates how the crushing strength of lithium orthosilicate pebbles varies with size and opacity, providing experimental data crucial for designing breeder blankets in fusion reactors.

Contribution

It provides experimental measurements of crush loads for pebbles of different sizes and opacities, and analyzes their Weibull distribution to aid in modeling pebble assemblies.

Findings

Crush load increases with pebble diameter.

Opacity significantly affects crush strength.

Crush load follows Weibull distribution.

Abstract

Crushing strength of the breeder materials (lithium orthosilicate, $\rm{Li_4SiO_4}$ or OSi) in the form of pebbles to be used for EU solid breeder concept is investigated. The pebbles are fabricated using a melt-spray method and hence a size variation in the pebbles produced is expected. The knowledge of the mechanical integrity (crush strength) of the pebbles is important for a successful design of breeder blanket. In this paper, we present the experimental results of the crush (failure) loads for spherical OSi pebbles of different diameters ranging from $250~\mu$m to $800~\mu$m. The ultimate failure load for each size shows a Weibull distribution. Furthermore, the mean crush load increases with increase in pebble diameter. It is also observed that the level of opacity of the pebble influences the crush load significantly. The experimental data presented in this paper and the associated analysis could possibly help us to develop a framework for simulating a crushable polydisperse pebble assembly using discrete element method.