Sintering and creep behavior of Li2TiO3 pebble bed for breeding blanket of fusion reactor

Abstract

Tritium is generated in a breeding blanket by nuclear reaction between neutron from fusion plasma and the lithium in breeder pebbles. The securing of stable flow path of the purge gas inside the pebble bed is important because the generated tritium is extracted by the purge gas, which flows through the empty spaces inside the pebble bed. The sintering and creep phenomena of the pebble bed can affect the flow path of purge gas and the tritium extraction because of the formation of necking between the pebbles by sintering and deformation of the pebbles by creep. This study aims to investigate the starting temperature of sintering on the Li2TiO3 pebble bed and the creep deformation behavior of the Li2TiO3 pebble bed under various conditions such as compression pressure and holding time. The initial stage of the sintering phenomena on the Li2TiO3 pebble bed under applied compression pressure of 1 MPa was estimated at between 850 °C to 900 °C. However, densification of the Li2TiO3 pebble bed caused by creep deformation progressed despite initial stage of sintering. Therefore, from the viewpoint of stable extraction of bred tritium from the breeder pebble bed, it was recommended, that, to maintain uniform flow path of purge gas inside the pebble bed, the maximum operating temperature and pressure of the Li2TiO3 pebble bed be 800 °C and 1 MPa.