Understanding the mechanics of tritium breeding pebble beds

What is it about?

Due to neutron irradiation, solid breeder blankets are subjected to complex thermo-mechanical conditions. Within one breeder unit, the ceramic breeder bed is composed of spherical-shaped lithium orthosilicate pebbles, and as a type of granular material, it exhibits strong coupling between temperature and stress fields. In this paper, we study these thermo-mechanical problems by developing a thermal discrete element method (Thermal-DEM). The overall effective conductivity of the bed depends on the resulting compressive stress state during the neutronic heating. The thermal-DEM method proposed in this study provides the access to the grain-scale information, which is beneficial for HCPB design and breeder material optimization, and a better understanding of overall thermo-mechanical responses of the breeder units under fusion-relevant conditions.

Featured Image

Photo by salvatore ventura on Unsplash

Photo by salvatore ventura on Unsplash

Why is it important?

Understanding the thermo mechanics of pebble beds is important in the development of fusion energy systems. In various proposed systems pebbles of lithium ceramics are planned to be used to produce further tritium fuel. The performance of such pebble beds under extreme conditions of heat, stress and irradiation must be understood.

Perspectives

“

The development of high performance tritium breeding ceramics and the mechanical properties of pebble beds comprised of such ceramics under extreme conditions remain a key challenge on the road towards fusion energy systems of the future...

”