Behaviour of advanced tritium breeder pebbles under simultaneous action of accelerated electrons and high temperature

Abstract

h i g h l i g h t s • Irradiation temperature affects accumulation of radiation-induced defects (RD) and radiolysis products (RP). • With an increasing content of Li2 TO3 in the advanced pebbles, the concentration of accumulated RD and RP decreases. • The accumulated RD and RP annihilates around 423-773 K. • Mechanical properties of the advanced pebbles practically do not change after irradiation. Advanced lithium orthosilicate (Li4 SiO4) pebbles with additions of lithium metatitanate (Li2 TiO3) as a secondary phase are suggested as a potential source for tritium breeding in future nuclear fusion reactors. The advanced Li4 SiO4 pebbles with different contents of Li2 TiO3 were examined before and after simultaneous action of 5 MeV accelerated electron beam (dose rate: up to 10 MGy h −1) and high temperature (up to 1120 K) in a dry argon atmosphere. The accumulated radiation-induced defects (RD) and radiolysis products (RP) were studied by electron spin resonance (ESR) spectrometry and thermally stimulated luminescence (TSL) technique. The phase transitions were studied with powder X-ray diffraction (p-XRD). The microstructure and mechanical strength of the pebbles, before and after irradiation, were investigated by scanning electron microscopy (SEM) and comprehensive crush load tests. The obtained results revealed that the irradiation temperature has a significant impact on the accumulation of RD and RP in the advanced Li4 SiO4 pebbles, and with an increasing content of Li2 TiO3 , the concentration of accumulated paramagnetic RD and RP decreases. Major changes in the mechanical strength, microstructure and phase composition of the advanced pebbles were not detected after irradiation.