Composition containing aerogel substrate loaded with tritium

This patent describes a composition. It comprises: an aerogel or xerogel substrate loaded with tritium and a component capable of emitting radiation upon interaction of the component with beta particles emitted from the tritium, wherein the loading of the aerogel or xerogel substrate with tritium is performed by initially hydrolyzing the surface of the substrate and then subjecting the hydrolyzed substrate to tritium exchange, whereby tritium atoms replace hydrogen atoms of hydrolyzed surface groups, and wherein the composition is a volumetric source of radiation