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Abstract: As a ceramic material proposed for tritium breeding in a fusion reactor blanket, lithium orthosilicate (Li4SiO4) is being examined in view of the influence of water uptake on tritium release behavior. In this work, out-of-pile tritium release experiments were performed on Li4SiO4 samples that were transferred and stored under different moisture environments. The water content was measured on the samples that were treated in similar conditions. Effects of water adsorption on the chemical form and temperature of released tritium were investigated. It is found that with the water content increases, the gaseous tritium fraction decreases and the proportion of low-temperature desorption of HTO increases. The results of this study can be used later for engineering and design activities for fusion reactor blankets. [Copyright &y& Elsevier]

Abstract: Out-of-pile tritium release examinations of irradiated Li4SiO4 pebbles were performed in TRINPC-I experiments for evaluating material performance and verifying the system design. To generate tritium the specimens were irradiated with neutrons. Li4SiO4 pebbles were made by a freeze-drying method. In the experiments, concentrations of tritium in the form of tritium gas (HT+T2) and tritiated water (HTO+T2O) in the outlet streams of a reactor tube were measured separately with an ionization chamber and a liquid scintillation radiometer. The results show that the percentage of tritium gas (HT+T2) and tritiated water trapped by the breeder pebbles were about 72% and 19% of totally released tritium, respectively. Thus, more tritium was released in the form of tritium gas in this work. In addition to tritium trapped by the breeder pebbles, the amount of free tritium was also measured by breaking on-line a quartz capsule containing Li4SiO4 pebbles, the percentage of which was 9% of totally released tritium. The temperature peaks of tritium gas mainly appeared at about 477°C and 654°C, while the temperature peak of tritiated water appeared at about 402°C, under which most of tritiated water released. [Copyright &y& Elsevier]

Li 2 TiO 3 -Li 4 SiO 4 biphasic ceramic pebbles have been developed as an advanced tritium breeder due to the potential to combine the advantages of both Li 2 TiO 3 and Li 4 SiO 4 . Wet method was developed for the pebble fabrication and Li 2 TiO 3 -Li 4 SiO 4 biphasic ceramic pebbles were successfully prepared by wet method using the powders synthesized by hydrothermal method. The tritium release properties of the Li 2 TiO 3 -Li 4 SiO 4 biphasic ceramic pebbles were evaluated. The biphasic pebbles exhibited good tritium release property at low temperatures and the tritium release temperature was around 470 °C. Because of the isotope exchange reaction between H 2 and tritium, the addition of 0.1%H 2 to purge gas He could significantly enhance the tritium gas release and the fraction of molecular form of tritium increased from 28% to 55%. The results indicate that the Li 2 TiO 3 -Li 4 SiO 4 biphasic ceramic pebbles fabricated by wet method exhibit good tritium release property and hold promising potential as advanced breeder pebbles. [ABSTRACT FROM AUTHOR]

Abstract: Li4SiO4 (lithium orthosilicate) is an important tritium breeder for fusion blanket concept. In test blanket module (TBM) design of China, Li4SiO4 ceramic pebbles have been selected as the first candidate material of tritium breeders. The fabrication process and properties of the pebbles have been investigated. Wet method is used to fabricate Li4SiO4 ceramic pebbles. XRD results show that Li4SiO4 with a high phase purity has been prepared by wet method. SEM photographs indicate that the pebbles have porous structure and small grain size. Li4SiO4 ceramic pebbles, which were sintered at 1020°C, have good properties, such as small diameter (0.5–0.8mm), high density (over 80% TD), good sphericity (1.02) and large crush load (a.v, 20N). The results show that Li4SiO4 ceramic pebbles can be successfully fabricated by wet method, under the appropriate conditions of solid/liquid ratio and sintering temperature. [Copyright &y& Elsevier]