A study on wall stresses induced by LaNi5 alloy hydrogen absorption-desorption cycles

Tritium is an element of considerable interest in the nuclear industry. Since it is radioactive, it needs to be used to be stored in a safe but easily recoverable manner. It is an isotope of H, and hence some of the techniques used for hydrogen storage can be employed, the safest being its storage in the form of a tritide. LaNi5 alloy has priority to be selected as tritium storage and boost material because of its attractive characteristic features. However, LaNi5 alloy's volume expansion ratio is up to 24% after absorbing hydrogen. The stresses induced by deformation lead to alloy's pulverization, which leads to self-compaction and concentration of stresses. In this paper, the relationships of wall stresses of LaNi5 hydrogen storage beds with cycle number of hydrogen absorption-desorption, loading of hydride beds, packing fraction and thickness of the beds' walls have been studied by using strain gauges. The experimental results indicate that the wall stresses increase with increasing packing fraction and decrease with thickening of the wall. The wall stresses slowly increase, up to a bed loading of about 0.4 hydrogen to metal atomic ratio. Different locations exhibit greatly different levels of maximal strain. The experimental results may play an important role for the understanding of stress accumulation mechanism.