Radioactive tracer such as a cell or tissue, or as a flow tracer to track fluid flow. Radioactive tracers are also used to determine the location of fractures created by hydraulic fracturing in natural gas production. Radioactive tracers form the basis of a variety of imaging systems, such as, PET scans, SPECT scans and technetium scans. Radiocarbon dating uses the naturally occurring carbon-14 isotope as an isotopic label. Isotopes of a chemical element differ only in the mass number. For example, the isotopes of hydrogen can be written as H, H and H, with the mass number at top left. When the
Tritium radioluminescence for night use and small lights (which need to be more reliable than battery powered lights yet not interfere with night vision or be bright enough to easily give away one's location) used mostly by military personnel fall under the latter application. Tritium lighting is made using glass tubes with a phosphor layer in them and tritium gas inside the tube. Such a tube is known as a "gaseous tritium light source" (GTLS), or "beta light" (since the tritium undergoes beta decay). The tritium in a gaseous tritium light source undergoes beta decay, releasing electrons that cause the phosphor layer