A research group led by Prof. WANG Haixia from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences has revealed the tritium release behavior of lithium titanate (Li₂TiO₃) breeder irradiated with fusion neutrons, which contributes to the optimization of the the solid blanket design in fusion reactors.

The results were published in Nuclear Materials and Energy and International Journal of Hydrogen Energy.

The tritium breeding and release behavior of solid breeders is critical to the design of solid blankets in fusion reactors. However, most breeder irradiation studies use fission neutrons, ion sources, or gamma sources, leaving a gap in the knowledge of 14 MeV fusion neutron irradiation. Therefore, experiments were performed on Li₂TiO₃ using a fusion neutron source to investigate the influence of high energy neutrons on tritium production and release performance in solid breeders.

In this study, a specialized tritium release system was developed to measure and collect tritium after fusion neutron irradiation. This system, with near 100% collection efficiency, incorporates tritium collection bubblers, automatic replacement technology, and catalytic oxidation. By minimizing tritium loss and monitoring the release of tritiated water (HTO) and tritium gas, the system allows investigation of tritium release behavior under various conditions like temperature, humidity, and heating rates.

Experimental results showed that at room temperature, a limited but visible amount of tritium was released from Li₂TiO₃ samples irradiated with fusion neutrons, indicating a self-healing behavior of defects. As the temperature of the samples increased, Li₂TiO₃ showed a tritium release peak, predominantly releasing HTO.

In addition, factors such as humidity in the sweep gas, different tritium measurement methods, and heating rates significantly affected the tritium release behavior.

"Our results provide new insights for understanding the influence of fusion neutron irradiation on the tritium release mechanism," said Prof. WANG Haixia.

Sample layout for 14 MeV fusion neutron irradiation. (Image by FU Xuewei)

Tritium release curve of Li₂TiO₃ in various temperature. (Image by FU Xuewei)